# Lead acid voltage sage



## Ampster (Oct 6, 2012)

As far,as I know the only thing you can do about with your existing configuration is to use less current, ie less accelerator. I am sure others will chime in about how Lithium Ion batteries tend to have less voltage sag.

Sent from my SM-N910T using Tapatalk


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## john61ct (Feb 25, 2017)

Yes, one of the huge advantages of LFP is a very flat V curve, even at high discharge rates.

A bigger bank may help a bit, but I think that's the nature of the beast with all the lead chemistries


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## 9852 (Jan 17, 2010)

Yea that's about what I thought. Well I guess I'll just use less accelerator, that will help.
So just like a gangster I'll go Slow and Low.


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## Sunking (Aug 10, 2009)

Assuming your connections are good and cable sized properly, there is nothing you can do about it. It is just a function of the current and battery internal resistance. 

Very familiar with Trojan batteries and the T-875 is a rather smallish 8 volt battery and when new fully charged has an Ri of roughly .005 Ohms so with 19 in series you have at least .1 Ohms of internal resistance plus any cable and connector resistance on top of that. The battery was designed for a 50 amp golf cart motor load. So at 50 amps you can expect at least a 5 volt sag, plus any cable and connector losses.

Typically Pb battery internal resistance is lower than lithium. However Pb batteries are a chemical reaction and not an Ion exchange. Thus a chemical reaction is slower and PB batteries cannot keep up with heavy discharges.


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## 9852 (Jan 17, 2010)

Ekthor, 
Ok lots of info, so I'll do my best to answer all of your questions.
1st ev specs:
94 Ford ranger, original curb weight was around 3200 pounds.
Ev curb weight is estimated at about the same, based on the weight of the truck minus the ice and all its components, plus the total weight of the batteries plus motor and transmission weight.
Electric motor: adc fb1 4001 
Controller: Curtis 1231c 144 volts 500 amps
Batteries: 19 Trojan t875
100% charged =160 volts
I only see the real bag sag when I'm using a lot of current fast.
Full throttle current is about 375 amps for 20 seconds or so before I let off if I'm driving it hard.


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## 9852 (Jan 17, 2010)

Ekthor, I agree about full charge voltage with my battery pack. I see 160 volts at full charge, and my meter is a chennic battery monitor, its set up to read 100% charged voltage at 160 volts, and 80% discharged at 149 volts, but if I'm really getting on it, the voltage can drop all the way down to 120, like I said it's not really a problem, because most of the time I'm driving to conserve power not eat it, its not a race truck. But today I just drove it like it was my f150 and noticed the sag.


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## 9852 (Jan 17, 2010)

Ekthor,
No I did not keep the clutch. It works just fine without it.
I can jump it out on the highway and do 70 for a few miles
If I drive it easy, I get about 48 miles per charge. Normal driving about 35 miles.


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## 9852 (Jan 17, 2010)

I just posted pics and specs in the garage


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## Sunking (Aug 10, 2009)

billhac said:


> Ekthor, I agree about full charge voltage with my battery pack. I see 160 volts at full charge, and my meter is a chennic battery monitor, its set up to read 100% charged voltage at 160 volts, and 80% discharged at 149 volts, but if I'm really getting on it, the voltage can drop all the way down to 120, like I said it's not really a problem, because most of the time I'm driving to conserve power not eat it, its not a race truck. But today I just drove it like it was my f150 and noticed the sag.


You cannot use a meter to determine SOC on a Pb battery. Completely useless, only a hydrometer can give you real time SOC on a working system. Voltage can only be used on a well rested open circuit PB battery.

As for charge voltage on the T-875 you should be charging to 188 volts. 160 volts is even lower than FLOAT Voltage @ 171 volts. Where are you coming up with 160 volts? You charge at 188 volts @ C/10 to C/8 (17 to 21 amps) until charge current tapers to 2 to 5 amps. Try looking at *Trojans Specs* and _*User Manual*_ page 19. If I were you i would get a good battery hydrometer and see where you are really at. My bet is you need a good EQ charge at 205 volts until Specific Gravity is equal. You are risking loosing your batteries from chronic under charge. 

Lastly as I stated earlier, Pb batteries cannot keep their voltage up under heavy loads like lithium can because it is a chemical reaction, and chemical reactions take time and does not happen at the speed of light like an Ion exchange in a lithium battery. If you are seeing 120 volts under load, you have a serious problem. 133 volts (1.75 vpc) under load would be completely discharged. Anything under 145 volts is serous. You need to figure out what is wrong before it is to late. FWIW never take the batteries below 50%. 

Good luck.


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## 9852 (Jan 17, 2010)

Sunking, I got the specs from the Trojan manual. It plainly states no load voltage is 8.48 volts x 19 batteries, you can do the math, that's resting voltage, so after the charge and not in use, so I had my battery monitor set for 160 for a full charge, and I don't know where you get to only discharge to 50 %, Trojan specs say 80% discharge is safe. As I said it really only happens at extreamy high current draw, if I use less accelerator I stay around 150. 188 volts is charge voltage, not full charge voltage, as soon as you turn off the charger that voltage will go down.


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## 9852 (Jan 17, 2010)

My charger charges at about 220 volts at about 20 amps, I know I'm getting a full charge, it was just strange because I didn't remember getting that much voltage sag when I brought it home at 120 volts. Maybe I have a bad battery but It don't feel like its losing any power to quickly


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## 9852 (Jan 17, 2010)

Btw, I did not use the batter monitor to determine the charge voltage, I use my fluke meter, then as I stated I had the monitor set up to read the voltage I got from my fluke, it works just fine.


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## 9852 (Jan 17, 2010)

Go back and read some of my other threads, I have already proven you don't have to spend a ton of money to have a great ev, this is not my first build, so I do know how to determine proper charge voltage.i was singly wondering if anyone else had this problem and if the found a trick for it aside from using less current


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## 9852 (Jan 17, 2010)

Well I just added water, but I have to admit I did not check voltages on each battery, but that is next, theses batteries are 7 years old so it's possible that they are going to start heading down hill on me


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## 9852 (Jan 17, 2010)

Yea man, I have the original sales receipt for the batteries, and all the date codes are the same. So they have had a good long run. However, I think the truck was converted and not driven much, because the batteries were strong when I brought it home. It was originally run at 120 volts, but I bought 4 more batteries for it, and every since then it just seems like it does not have the same range, you would think it would get a couple more miles range but not really. It's got to be one of the batteries I bought for it. I really haven't had the time to look at it real close yet.


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## 9852 (Jan 17, 2010)

Now I know someone is going to mention the fact that I'm running the Curtis controller at 152 volts nominal, but before I added that 4th battery to go up to 152, I did place a call to Curtis's service company to find out what the over voltage cut off was on the controller and explained to them what I wanted to do, the tech I spoke to confirmed that the over voltage cut off was 180 volts, so UNOFFICIALLY he said I could run it all the was up to 170 volts to be safe, as long as my controller was never on during the charging process. And I have a Spare controller just in case so I said what the hell, lets see what happens


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## john61ct (Feb 25, 2017)

billhac said:


> these batteries are 7 years old so it's possible that they are going to start heading down hill on me


Most definitely, and pulling down to 20% will lose you half the lifetime cycles compared to 50%.


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## 9852 (Jan 17, 2010)

Yea, it doesn't really go into overvoltage cut off to much in the manual, it says it has overvoltage cut off, but not what that voltage is. I'm having a bit of a heating issue myself, but I've been running my controller at 152 for weeks now without a problem, so I'm chalking my heat issue up to me running the truck hard and it being 110 degrees today, I'm going to cut back on the accelerator and see if that helps mine any. If not I'll be doing the same


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## 9852 (Jan 17, 2010)

Ok, it's 117 degrees right now here in Phoenix, I just drove my truck around the block, before I took off I checked the controller temperature it was 101 degrees, just sitting there, just as I got in the driveway I could hear the overtemp alarm going off again, my conclusion: 
ITS JUST TO DAMN HOT TO DRIVE THE EV. I'll have to start a thread on water looking a Curtis controller


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## 9852 (Jan 17, 2010)

Ekthor, I won't sell it, I think a person should have a spare controller for emergencies, even if you have a zilla or a soliton 1, just because you never know what could happen


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## Sunking (Aug 10, 2009)

Bilhac you are not understanding what I am telling you. 

You cannot use a SOC meter to determine the battery SOC. It is completely useless. Only time you can use voltage to determine a Pb battery SOC is if the battery is at room temps, OCV and rested for many hours. Even then it is only Ball Park. 

What you are seeing with Voltage Sag is perfectly normal and expected. Your results are extreme because your 7 year old batteries were ready to be replaced 4 or 5 years ago, especially if you have been discharging to 80% DOD. 

I design a lot of Solar Off-Grid Battery Systems professionally and have been in the Telecom Battery plants sector for 40+ years. I have worked with all major battery manufactures and their largest customer for the last 15 years. A small battery order for me is $200,000. 

In a solar system you design it for no more than 20% DOD per day and never allow them to go below 50% DOD. The reason is simple, CYCLE LIFE. Once you below 50% DOD the lead sulfate crystals begin harden and cannot be dissolved back into solution . Sulfated batteries are responsible for 90% of all battery failures. If you were to look at Trojan Cycle Life vs DOD you will understand. The T-875 is a Low End Line like the T-105. They are a 2 to 3 year battery if you limit discharge to 50% DOD 

If discharged 20% DOD you are looking at roughly 1500 cycles, To 50% DOD around 600 cycles. Go down to 80% DOD. If you go to , you are looking at 300 cycles. Yeah it is safe to go down to 80% DOD, and good for Trojan with frequent replacements doing so.

To make matters worse that T-875 is rated at 170 AH at the 20 hours discharge rate (9-Amps) With PB batteries Mr Peukert and his Law will rob you blind if you discharge faster than C/20 or 9 amps. You are cruising roughly at 1C rate of 80 to 100 amps. When you apply Peukert's Law of a 1C discharge rate you are turning your 170 AH battery into 50 AH and at 50% DOD is only 25 AH usable. 

So what you are seeing is expected with old batteries that needed replaced 4 or 5 years ago. Couple that with the abuse and you are lucky they will even hold a charge. They are sulfated and cannot accept or give up much charge. Time to replace those boat anchors.


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## 9852 (Jan 17, 2010)

Sunking, I think it's you that is not quit understanding, the batteries were never abused,at least not until I got it, I was getting a forty mile range out of the car when it was at 120 volts, now at higher voltage I seem to be getting a bit less but not much, just because the batteries are older don't assume they are sulfated, as I've said the original owner never drove it much, hence the batteries do not have a lot of charging cycles on them yet, now I'm sure even a battery that is sitting on a shelf for years will loose some capacity over time, but not that much, I do allow for peukert but come on really, I'm still getting a 40 mile range, if it had a 25 amp hour rating because of peukert the truck wouldn't go 10 miles. I do know how to calculate ev range, I'm only asking if anyone else has experienced this or not, this is my 3rd ev, all done with lead acid batteries, so I'm pretty sure I could tell if the batteries need to be replaced, and they are not there yet. I will admit that this might be a sign of new batteries to come but not yet, no, not yet.


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## 9852 (Jan 17, 2010)

By the way, I agree with you about sulfated batteries not holding or giving up a charge, but right now the battery voltage is 152 from my fluke meter, which is an industry standard voltage meter, and they are at 152 volts after a very hot 12 mile drive, does that sound like the behavior of sulfated batteries?


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## 9852 (Jan 17, 2010)

Sunking, exactly what do you use to measure the state of charge of your batteries if not a voltage meter? I mean that's what has been used for years with out any issues? That is why battery companies give you the state of charge statistics in voltages, like this chart from Trojan battery company 
http://www.trojanbattery.com/pdf/datasheets/T875_Trojan_Data_Sheets.pdf


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## 9852 (Jan 17, 2010)

My truck works just fine as did my Eneon and my spitfire ev with a voltage and amperage meters


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## brian_ (Feb 7, 2017)

billhac said:


> ...
> 94 Ford ranger, original curb weight was around 3200 pounds.
> *Ev curb weight is estimated at about the same, based on the weight of the truck minus the ice and all its components, plus the total weight of the batteries plus motor and transmission weight.*
> Electric motor: adc fb1 4001
> ...


The logic makes sense but the conclusion does not seem possible to me - have I missed something?


Only the original engine, exhaust, cooling system, and fuel tank have been removed. 
19 Trojan T-875 batteries at 63 pounds (29 kg) each have added 1197 pounds (551 kg)... plus a 65 kilogram (143 lb) motor and the controller, etc.
The electric additions total over 1400 pounds. No Ranger engine weighed anywhere close to three quarters of a ton. Your truck is probably several hundred pounds heavier than the gasoline original. Right?


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## 9852 (Jan 17, 2010)

Brian, don't believe so, I looked up original curb weight before posting the conversion weight in the garage, all the info on it says it was originally around 3200 pounds, but I'll look again to make sure.


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## 9852 (Jan 17, 2010)

Specs from the auto channel:


Base Price $ 11,995
Price As Tested $ 13,640
Engine Type I-4, 8-v, sohc, mpfi
Engine Size 2.3 liter/140 cid 
Horsepower 112 @ 4800 
Torque (ft/lbs) 135 @ 2400 
Wheelbase/Length 108"/185"
Transmission five-speed manual w/overdrive
Curb Weight 2930 lbs.
Pounds per Horsepower 26.2
Fuel Capacity 17 gal.
Fuel Requirement Unleaded regular (87 oct) 
Tires P225/70R16 all-season
Brakes vented disc/drum ABS std rear only 
Drive Train Front engine/rear drive

PERFORMANCE

EPA Economy - miles per gallon
city/highway/observed 23/28/26.4
0 to 60 mph 10.2 sec
1/4 mi (E.T.) 17.8 sec
Coefficient of Drag (Cd) .40 
This is just a quick search, it's for the 2.3 liter 4cyl engine, mine was the 3.0 liter, about 150 pounds more engine a bigger tank, more exhaust pipe, and let's not forget the engine is not aluminum it was all steal, steal exhaust manifolds, so I don't think I'm heavy, if anything I think I'm a little lighter.
But also I did not do the conversion, I bought it converted, but I did do reasearch on curb weight.


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## 9852 (Jan 17, 2010)

Found this spec too;

https://www.kbb.com/mazda/b-series-regular-cab/1994/b2300-short-bed-specifications/ , 
I mean I guess it's possible I'm a couple hundred pounds heavier, I don't think so, but even so, payload specs are around 1250 pounds.


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## 9852 (Jan 17, 2010)

Also, the max gvwr is 4660 lbs.


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## brian_ (Feb 7, 2017)

billhac said:


> Brian, don't believe so, I looked up original curb weight before posting the conversion weight in the garage, all the info on it says it was originally around 3200 pounds, but I'll look again to make sure.


Maybe I've misunderstood... it looks like you're saying that the gasoline Ranger weighed 3200 pounds and the EV conversion weighed *the same* 3200 pounds. It does not seem possible that the conversion does not change the weight, given the components used.

If a 2.3L 2WD manual transmission weighed 2930 pounds then I could see how this 3.0L V6 weighed 3200 pounds; however, the electric conversion would still weigh more than 3200 pounds... because even the iron-block gas engine with accessories didn't weigh anything close to the 1400 pounds of the electric components.

WolfTronics noted in his battery upgrade thread that his Solectria E-10 has a curb Weight of 3959 lbs with around 1200 lbs of that being lead-acid batteries... and that's with no transmission. A Ranger is very close to the S-10 in size and weight, so with a transmission and the same battery weight it would be reasonable to expect a similar weight.
1995 Solectria E-10 Specs

I didn't see this truck at first in the DIY Electric Car Garage, because I was looking for a Ford Ranger. The only 1994 Ranger is shown as _Forklift Guy_'s, with different components. I now realize that this must be billhac's "Evrc "... which is for a Mazda B3200 (yes, I understand that Mazda sold Rangers as Mazda B-Series; if the donor was a 3.0L V6 this should have been a B3000) and says that the finished weight is 3200 pounds - same as the likely donor vehicle stock weight.

It's not really important - the weight just guides expectations for performance - including energy consumption - and will be taken as a precedent for others doing conversions.


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## brian_ (Feb 7, 2017)

billhac said:


> Found this spec too;
> 
> https://www.kbb.com/mazda/b-series-regular-cab/1994/b2300-short-bed-specifications/ ,
> I mean I guess it's possible I'm a couple hundred pounds heavier, I don't think so, but even so, payload specs are around 1250 pounds.





billhac said:


> Also, the max gvwr is 4660 lbs.


What these specs mean is that the gas truck (if a V6) weighed about 3400 pounds (perhaps only with all options), and that the several hundred pounds that the conversion has added to the truck have reduced the payload to a few hundred pounds; for instance, a 3400 pound gas truck converted to a 4000 pound electric truck - still with a 4660 lb GVWR - has a remaining payload of 660 pounds.

In other forums, unrelated to EVs, I've noticed that people often have no idea what their travel trailers or tow vehicles weigh... even when they have been careful to keep track of what they have added and they're confident that they know the result. I use a highway scale (the ones used to enforce commercial truck weights and axle loads) to find the actual weight.


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## Duncan (Dec 8, 2008)

Hi Brian
I agree about weights - The only useful actual weights are from weigh stations 
Which are actually very common and all of the ones that I have used have weighed my vehicles free!

Anywhere that sells stuff by weight, - gravel, fertiliser, grain will have a weigh station
Also your local rubbish dump or transfer station will have one

I just wish I had realised how easy it is to get stuff weighed back when I was playing with my mini


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## john61ct (Feb 25, 2017)

Batteries should be replaced when a 20-hour load test shows they have lost 20-25% their original AH capacity C. That is the only reliable State of Health measure.

You tell they are full when Absorb stage amps drop to below 2% of C, some mfg spec lower.

A proper SoC meter measures AH out via a shunt.

Voltage is a very rough guesstimate even after 12+ hour resting.


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## 9852 (Jan 17, 2010)

Duncan, + 1 on that, 
I think there is a gravel yard not far from me, I'll just take it and find out, I just saw some notes in my conversion folder that mentioned the weight, that where I was getting it from. 
John, yes but its not rocket science here, its car conversion, that's it, every charger that I have ever used measured soc by voltage, after that preset voltage they turn off, its simple as that, the battery manufactures have already did all of the 20 hour testing, the voltage meter is a guide to help the average joe to figure out soc. That's why we use lead acid in the first place. Lifepo4 cells are nice but they are not for everyone, I can see why you would want a better way to keep track of soc with those, but that is yet another reason in a long list of reasons that I use lead instead. My voltage meter works just fine thanks


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## 9852 (Jan 17, 2010)

Brian,
Your right I just call it a Ford ranger, but in my defense they are the same truck, the b series trucks were made by Ford for Mazda, all parts are interchangeable, except trim packages. That's it. So hence the name Evrc,it stands for electric ranger clone.


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## Sunking (Aug 10, 2009)

Billhac Voltage is useless on a working battery. That means being charged or discharged. At best SOc voltage is only a BALLPARK guestimate on a fully rested battery. That means disconnected from everything and allowed to rest for many HOURS. Look it up that is exactly what TROJAN is telling you and what OCV means. I can make a 8 volt brand new battery fully charged read 7 volts, or I can make the same battery fully discharged read 10 volts. Batteries have two life times. Cycle Life and Calendar life. Whichever comes first. Calendar life is basically the Warranty period. The T-875 has a 2-year warranty. You voltage is sagging because they are basically shot and sulfated. They make battery voltage monitors for folks who do not know the limitations. It is called making money. 

Voltage sag is the product of *Current* flowing through the battery *Internal Resistance* called Ri. The voltage of a *Discharging Battery = OCV - [Current X Ri]*

OCV = Open Circuit Voltage of a RESTED BATTERY. 

So figure it out why you have so much Voltage Sag. A Trojan T-875 in new condition has an Ri= 0 .004 Ohms. You have 19 batteries in series for a total Ri= 19 x .004 = *.076 Ohms.*. Now do some math so you understand. If your battery voltage sags from 160 volts to 120 volts under load means 1 of 3 things, or a combination of the 3.

1. You are pulling [160 - 120 volts] / .076 Ohms = *526 amps* which is not possible without melting the Battery Term Post off. That would be 3 times the max safe designed current load. 

2. Your battery are sulfated and needed replaced a long time ago. The Ri is way too high. 

3. Poor cable connections or undersized cables. 

Bet you anything your your batteries are shot. Time to spend a lot of money.


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## 9852 (Jan 17, 2010)

Sunking, your wrong about a lot of things, but more important you did not read, I said that the manufactures have done the math for us, and I said that is why we use volt meters, because it gives us an ESTIMATE OF soc, had you have read my last posts you would have known that. 
Now, here is the important reason why you are wrong, you are not here to look at the battery pack, iv said repeatedly that the batteries are not sulfated, but you just keep insisting, so if you don't like my old working batteries feel free to gift me more.
Now here is where you are right, well kinda anyway
As I have stated, when I brought the car home it was at 120 volts, I added 4 batteries to make it 152 volts. Now here's the good part because I know you want me to be wrong, but.........
I realized that the cables that I used to add the 4 batteries were undersized. Actually I knew they were different when I put them on and was just hoping it would not make a difference, but after changing them to the proper sized 2/0 cables, the voltage stays constant at around 158-160 ,( 8.49 volts per battery x 19 batteries, resting voltage as you have stated I know how you like using voltage to measure soc) volts until at around 38 miles and then it starts dropping depending on current draw from my foot. Thanks for your help, but as I have stated to you repeatedly my batteries are fine, and now the problem is solved so no need to keep replying to the thread.


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## john61ct (Feb 25, 2017)

You keep saying they are "fine", but all the evidence points to you either being wrong about that, or using that word for a condition the industry defines as scrap metal.

The only objective measure of your bank's health is a standard 20-hour load test.

If you haven't done that, then you have no idea of their actual condition.

When you have had that done, and it comes back say over 85% of their AH rating when new, then you can say "they're not scrap yet" with credibility.


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## 9852 (Jan 17, 2010)

What the he..... is wrong with you people? Do you own a battery store? Why do you think I'm saying they are fine? All 15 of the original batteries were load tested before I bought the damn truck, I should not have to explain that, and besides I said the problem is solved, thanks for the help but it's WAS NOT THE DAMN BATTERIES, I know how to take care of them, and the original owner worked for a golf cart company here in Phoenix, so they were, let me repeat it so everyone understands, they were tested periodically, and tested before I brought the truck home. 

I was away for a few years so I'm confused, what happened to this site? When I first came here in 2007 this site was a wealth of info, for people to learn how to build a budget, reliable everyday driving ev, now it seems like the only help you give is go buy more of. Gesse, I had it figured out this morning with a quick drive to the shop that the original owner works at, 

This site is supposed to be for people to learn from pioneers like M. Paul Holmes and a few others to help people save money and share experiences, which is what I was asking, in the original post, but instead I get country club people wanting to show off there crap, some who don't even have an ev but want to tell me my batteries are bad.
If this is the help that this site gives now I'm sorry I want no part of it. Ill just get with some friends and start our own site that will actually help people looking for tips or tricks! Like my original question was, or looking for info on how to get started cheap,

I've been talking about doing this for a while now, so thanks for helping me make up my mind.


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## brian_ (Feb 7, 2017)

billhac said:


> Brian,
> Your right I just call it a Ford ranger, but in my defense they are the same truck, the b series trucks were made by Ford for Mazda, all parts are interchangeable, except trim packages.


True!



billhac said:


> So hence the name Evrc,it stands for electric ranger clone.


 I like the name!


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## Sunking (Aug 10, 2009)

billhac said:


> What the he..... is wrong with you people?


Nothing wrong, I have worked professionally with batteries for 40+ years. I am a Professional Engineer and sit on IEEE Battery committee for 25 years. Worked with every battery manufacture worth naming including Trojan. I am telling you your batteries are shot, done, kaput. You are describing in great detail your batteries are sulfated. Deal with it and time to spend a lot of money.

No one can help you fix dead batteries.


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## brian_ (Feb 7, 2017)

If it makes you feel any better, all the discussion of internal resistance of the batteries may have subconsciously helped you realize that the source of the voltage sag was excessive resistance... but in the interconnects.


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## Sunking (Aug 10, 2009)

brian_ said:


> If it makes you feel any better, all the discussion of internal resistance of the batteries may have subconsciously helped you realize that the source of the voltage sag was excessive resistance... but in the interconnects.


That is what I am trying to get through to him. He wants no part of it. 

Bill listen to yourself. You claimed you did a LOAD TEST. I have no idea what the results were when you did the LOAD TEST, or if you even really did a proper LOAD TEST. What I do know know is you do not even know what a LOAD TEST is. Because if you did, you would know your batteries are failing a LOAD TEST every time you press down on the accelerator. That is what Voltage Sag is and is caused by excessive Battery Internal Resistance. Get your noodle wrapped around that. 

What causes a battery internal resistance to rise. Everything like age, abuse, neglect, normal wear and tear, and all a result of Sulfating batteries. It happens sooner than later. 

There are two real test your batteries will not pass. You do not have to take my word for it. Try it yourself with just one or two batteries. You live in Phoenix or so you claim. Phoenix has half a dozen Trojan authorized dealers throughout the metro are. In case you did not notice Phoenix has a ton of golf courses and you are using golf cart batteries. 

Take one or two batteries to any of the authorised Trojan dealers and have them test your batteries. They have a nice little battery tester they designed, and it takes a few hours to test a battery. In your case just a couple of minutes to run the 4 test.

1. They will charge it at 50 amps until charged. Your your will fail quickly as the charge will be fooled into thinking the batteries are charged up. When they hit it with 50 amps charge current, the voltage will spike up because Ri is high.

2. They will measure Ri and compare it to what they are known good values for that model battery. For a T-875 is .004 Ohm's. That means anything greater than .008 Ohms will fail. Yours will fail that test. 

3. If test 1 and 2 are OK they will do a proper Load Test. For a T-875 they will apply a 75-Amp load and measure the battery voltage under load. If the battery still has useful life the voltage should not sag more than 0.5 volts or 7.9 volts. Anything less than 7.9 volts fails and is caused by Internal resistance being to high. Your will fail. 

4. Last test is the most important test of all, Capacity Test. They will discharge a T-875 at 50 amps until the voltage drops to 7.0 volts which is 1.75 vpc, a completely discharged cell under LOAD. From that wil tel them how many AH capacity is left in the cell. Now this is where Trojan spins the numbers a bit. If the batteries are still under Warranty pass/fail line is 50% of rated capacity. Anything above 50% is a PASS. If out of warranty they use BCI. IEEE, and Industry standard of 80% rated capacity. So if your batteries were 1-day out of warrant, measured 79% would Fail. Your batteries will not even come close to 50%. 

But at least you will know. After they test and give you the results, they will introduce you to a SALESMAN. 

You may not like what I say, but it is fact you are in denial of. You wanted to know what is wrong, now you know. You just do not like the answer. Not my problem.

EDIT NOTE:

Billhac if you really want to learn something and understand, you can easily measure the Ri of your battery pack, or really any individual cell in the pack. Anyone can do it with there with pencil, paper, volt meter, motor controller current meter, and a simple math formula. Millennials will also need a calculator. 

1. Connect Volt Meter directly to battery term post, not the controller input so you are not measuring cable resistance on top of battery resistance. 

2. With vehicle in idle condition with and no current flowing measure battery voltage and record it. Call it VNl (Voltage No Load).

3. Depress accelerator, establish a constant speed quickly and record Voltage and Current at the same moment. Call the Voltage Vl (Voltage loaded) and Current C.

4. Determine *Ri = (VNl - Vl) / C*.

5. For Millennials use your calculator to determine Ri. 

Considering you have 19 x T-875's wired in series a PASS Result would be *.1 Ohm or Less*. Bet your result is 5 times or higher than that. That is why you have by your words Voltage Sage. There you have it a real A real LOAD TEST.


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## john61ct (Feb 25, 2017)

​Fot those not using a bank which can just be taken for free testing, or who want to know how to DIY a 20-hour Load Test that at least comes close to what you'd get taking them to a pro DC electric shop, using gear costing thousands of dollars

--------
From Compass Marine's RC, aka "Maine Sail"

http://www.pbase.com/mainecruising/programming_a_battery_monitor


#1 Fully charge battery then allow it to rest, disconnected, for 24 hours

#2 Make certain battery temperature is between 75F & 80F

#3 Apply a DC load that = Ah Capacity ÷ 20 (small light bulbs and/or resistors can work)

#4 Connect an accurate digital volt meter to the positive and negative battery terminals

#5 Start DC load and a stop watch at the same time

#6 As battery voltage drops, during discharge, adjust the DC load to maintain as close to the C÷20 rate as is humanly possible

#7 Immediately stop the discharge test when battery terminal voltage hits 10.499V

#8 Note the hours and minutes of run time on the stop watch and figure your percentage of 20 hours that it ran. This is your batteries Ah capacity or state of health as a percentage. For example if a 100Ah battery ran for 16 hours it is at 80% of its original rated capacity. Flooded lead acid batteries are considered “end of life” when they can no longer deliver 80% or more of their rating.

#9 Recharge the battery immediately at the 20 hour rate. Follow this up with equalization level voltage and measure specific gravity until all cells match. (not for non-Lifeline AGM or GEL). A long slow recharge can have a slight reforming effect on flooded batteries and can actually recover some lost capacity.

"But RC isn't 10.5V bad for my batteries?"

A once yearly discharge test, done correctly, is arguably less damaging than taking your battery to 50% SOC and leaving it in that range for a day or two or the continual PSOC cycling the average boater thinks nothing of. Regular PSOC cycling is more damaging than a once or twice yearly Ah capacity test done correctly. A capacity test, done correctly, simply counts as another deep cycle.

WARNING: The only time your batteries should regularly be taken below 12.1V is during a capacity test. For regular house use, at your average house loads, your deepest loaded voltage should ideally not dip below 12.1V or better yet 12.2V. Unless you are running short duration high load device such as an inverter, windlass, electric winches, thruster, water maker etc. don't let your bank voltage dip below 12.1V. For certain situations, such as an off-shore passage or open ocean racing discharging to 70-80% DOD is acceptable provided the batteries receive a proper charger as soon as you get to the destination. Regularly discharging below 50% SOC on a regular basis in a PSOC environment drastically shortens battery life when compared to 50%.

Firefly & some GEL batteries would be an exception for regularly discharging below 50% SOC.


--------
How do I conduct an approximate 20 hour capacity test?

#1 Allow battery to attain a steady 75-80F temperature

#2 Fully charge battery and equalize if it's capable

#3 Let the battery rest for 24 hours

#4 Apply a DC load for 2 hours that = Ah Capacity ÷ 20 (small light bulbs and/or resistors can work)

#5 Allow the battery to rest for at least 10 hours at 75-80F (24 hours is significantly more accurate)

#6 Check specific gravity or resting open circuit voltage and compare to manufacturers SOC tables

#7 Use basic math to determine the approximate Ah capacity. For example, a 100Ah rated battery has been discharged at 5A for 2 hours. This means so you removed 10Ah's of capacity. If the battery was in perfect health specific gravity readings or open circuit voltage readings should show the battery at 90% SOC. If SG and OCV only show the battery at 60% SOC then the battery has lost approx 30% of it's Ah capacity.

This is an approximation only and NOT an accurate Ah capacity test. Variances can be anywhere from 10-18% off an actual 20 hour capacity test depending upon your particular battery.


--------
Also:

http://www.cruisersforum.com/forums/showthread.php?p=2386436

https://forums.sailboatowners.com/index.php?threads/specific-gravity-vs-actual-ah-capacity.185414/

Thanks SK for that detail about Trojan policy, actually LOL that their warrantee would pass a battery degraded 49%!!


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## Sunking (Aug 10, 2009)

Yes John that is how any battery is CAPACITY TESTED. But no one would common sense would use a C/20 load. Who the heck wants to sit around up to 20 hours and watch paint dry. That is why pros use more like 1C up to 3C with a LVD to run the test in an hour or two. You have to adjust for Peukert Factor which most quality battery manufactures provide for FLA batteries. Not needed for lithium discharging up to 1C. Example Trojan list the C/2 rate of the T-875 at 110 AH @ C2. So you use a 55 amp load and run the timer. The Trojan Tester uses 50 and 75 amps FWIW.

Now if you want to DIY aka James Bond orr MacGyver, use Car Head lights, or my old favorite before I bought a PL8 6 years ago is wifey's old Blow Dryer Heater Element. Us RC toy guys use them all the time to discharge are LiPo packs for storage or measure capacity. 

But geeze a C/20 load is just plain silly. Who wants to sit around and watch paint dry for 20 hours?

For those who do not know who Mr Peukert is, he is a thief that will rob you blind. Peukert's Law states: _Change in capacity of rechargeable lead–acid batteries at different rates of discharge. As the rate of discharge increases, the battery's available capacity decreases_

Well if you are not familiar with Peukert's Law may not think that is a big. Here is a SPEC SHEET on a ROLLS S-290 a 6-volt 230 AH battery, equivalent to a Trojan T-105 a 6-volt 225 AH gold cart battery. Any good battery manufacture will publish Peukert's chart. If you rFLA manufacture does not, run away. OK 230 AH is the C/20 rate of 20 hours aka C/20 at 11.5 amps. OK the same battery rated at 1C or 83 amps is a 83 AH battery, or at C/100 is 2.93 amps is a 293 AH battery. FWIW a golf cart battery is designed to run at 50 to 60 amps cruise. So that same 230 AH battery is really 120 AH battery at C2 or C/3 rate. About 1 hour cruise time. You just thought you paid for 230 AH which is FALSE. 

Now if you know what you are looking for on th eRolls Spec Sheet you can determine Ri = .004 Ohms from the MCA rating


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## john61ct (Feb 25, 2017)

Note there is an abbreviated version above as well. But the full 20-hour version is really **the only** way to get SoH accurately, other than paying a shop to do it for you of course.

I know dozens of people who do this when their House bank is new, and then at least every year as part of normal maintenance.

Some are now well into 12-15 years with banks still at 80+% capacity.

Most LFP owners banks are still well above factory rated when-new AH, some getting up to ten years, and expect to get well past twenty.

The kind of usage pattern EV owners impose of course can't get the same results, but to me it's well worth trying to emulate as many of such routines as possible, to try to get as good longevity as possible.

Especially IMO when you're trying to recycle stuff that is likely already seriously depleted.

And it's not like you are manually watching the dials yourself, see the lower links for automating with smartphone apps.

Plenty of things you can do while it's running, I never have less than a week's worth of computer-based projects queued up myself. Or plenty of chores nearby to catch up on that can get done a few minutes at a time.


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## john61ct (Feb 25, 2017)

For those maybe also interested in House bank or other 12/24V usage, SmartGauge is the only SoC battery monitor that dynamically adapts its % SoC readings to account for the inevitable walkdown in capacity.

With shunt-based coulomb-counting monitors like Bogart's Trimetric or Victron's BMV-702, you need to recalibrate them to the new AH capacity *at least* annually, using the (yes tedious) 20- hour test outlined above.


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## Sunking (Aug 10, 2009)

john61ct said:


> Note there is an abbreviated version above as well. But the full 20-hour version is really **the only** way to get SoH accurately, other than paying a shop to do it for you of course.


John no offense but that is just plain not true or accurate. Common sense ought to tel you otherwise. That is why quality FLa battery manufactures publish Discharge Curves. If you apply Critical Thinking skills, you will quickly understand how flawed that logic is. 

1. You can test a battery capacity at any rate you want with great accuracy. But you must apply Peukert Discharge curves. That is why quality battery manufactures publish them Battery manufacturers play number games with AH capacity. You have to know what Discharge Rate they are using and specifying. Consumer grade batteries are usually rated at C/20. Fine if you are using that battery for a solar battery with 3 to 5 day reserve capacity capacity, and do not know any better like most consumers. Commercial and Industrial batteries are rated at C/4 to C/8. A C/4 battery can be rated at 150 AH @ C/4 or 230 AH @ C/20. You had better know the rules of the game or you are in for a surprise and education you may no tlike and learn the hard way. 

Example most DIY EV's discharge at around 1C when cruising, and many time more than that accelerating. Common sense tells you that is fact. If your EV only has a 40 to 60 mile range, means only has 1 hour cruise time or 1C discharge rate. You get a Nasty Education when you buy that 230 AH battery rated @ C/20 to learn it only has 83 AH @1C. Especially disappointing when you can only use 50 to 80% of that 83 AH when you thought you had 230 AH. 

2. When you do a AH Capacity test, you must stress the battery with real world application. In an EV you do not discharge at C/20. You discharge again at very high rates of C/2 to 5C. If you test at C/20 you get no usable results and have to spend hours to find out the battery is shot. Why? You had better know the answer. 

Answer is a battery with lost capacity is a battery with High Resistance. Not only do you want to test Capacity, but you want to *Load Test* the battery at the same time with *real world application*. If you were to test at say C/4 or higher test current on a tired battery, the test is over in a mater of a minute or two. You will not know the capacity or care what it is because it cannot supply a heavy load that an EV puts on the battery. The high current of C/4 or greater will cause the voltage to sag immediately, thus terminating the test. You do not care what the capacity is if the dang battery will not pass a valid real world load test. Kids on bicycles could accelerate quicker, go faster, and longer distance. Real world test produce real results. 

3. Lastly it is impossible for a DIY to perform a accurate Capacity Test with any FIXED LOAD. Again you should be able to figure that out real fast if you can add 2 + 2 and apply critical thinking skills. Real simple to measure AH accurately you must use a *CONSTANT CURRENT LOAD*. That is impossible with a fixed load. At best all you get is a Ball Park number +/- 20%. 

Example with simple 2 + 2 math. Assume a 12 volt 200 AH battery with a fixed load of 1.26 Ohm's. When the battery is fully charged and resting at 12.6 volts, when you start the test current = 12.6 volts / 1.26 Ohms = 10 amps a perfect C/20 load. 5 minutes later the voltage drops as the battery discharges resulting in lower current. After 22 hours you finally hit 10.5 volts. What is the current? 10.5 volts / 1.26 Ohms = *8.33 Amps*. You gotta problem it should be 10 amps. 

Now you apply an invalid formula and logic. AH = A x H, or 22 hours x 10 amps = 220 AH. You think eureka I paid for a 200 AH battery at it is 220 AH. For the formula to be true and accurate, one variable has to be constant. Can you guess which variable has to be constant? Did you say Current? Impossible with a fixed load resistance.

Bottom line here is Billhoc has a bad battery. He does not understand the very basics. He claims the batteries are good, but his own words say the exact opposite. He claims the battery is fully charge and measure 160 volts at idle. However he says when he accelerates and cruises the voltage Sage to 120 volts and ask why? Simple answer is his battery are shot and screaming at him. He just cannot hear them screaming or willing to listen to someone who can hear them. He just does not want to hear the truth and admit he does not understand.


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## john61ct (Feb 25, 2017)

If you benchmark at whatever given discharge rate when the bank is new, you then can see how fast they're declining by comparing again later.

I prefer the 20 hour rate as that is the usual standard, and also many people don't establish that initial baseline when the bank is new. 

If a bank fails that test (lost 20-25% rated AH capacity), then of course it would fail the more strenuous one at a higher discharge rate.

Also with lead chemistries those much higher rates are more destructive, as are EV usage patterns in general.


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## piotrsko (Dec 9, 2007)

Stop your charging at your target voltage and every several cycles full charge to 14.24 a battery then do the water heater discharge.

Racers don't care about battery life. 

A shorted fla will deliver crazy amps until something melts, usually before internal resistance becomes an issue.


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## Sunking (Aug 10, 2009)

john61ct said:


> If you benchmark at whatever given discharge rate when the bank is new, you then can see how fast they're declining by comparing again later..


John I will give you a tip every Utility, Telephone, and Cell Phone Tower operator uses to benchmark batteries. Even DIY can do it. All it takes is a few minutes. 

Measure your battery Ri when new after few cycles. Makes no difference if they are Pb or LFP. You can use your motor controller shunt and a volt meter as I already described. Only takes a few minutes. There is a direct correlation between Ri and Capacity. 

There is a company called Midtronics that manufactures Battery Conductance Meters Every utility uses them. What is unique about them is they use 75 Hz to measure Impedance. All others use 1000 Hz. 75 Hz gives you real close to DC Resistance. Point here is Midtronics has a database of hundreds of thousands battery Ri plots and the data clearly shows when your Ri goes up 100%, you have lost 30% of your capacity. Naturally you have also doubled your Voltage Sag and the batteries can no longer deliver high current loads or pass a LOAD TEST.

Nothing special is needed. Just working knowledge and common sense. No grueling 20 hour worthless test watching paint dry. No utility companies do capacity test anymore. Cost to much, takes to much time, and is archaic.


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## Sunking (Aug 10, 2009)

ekthor said:


> Sunking has provided what perhaps is the most valuable information regarding Peukerts and real capacities in practice based on *vendor* information. Thank you!


You are welcome



ekthor said:


> As I said earlier in this threat, NETGAIN itself has found racers taking 1400Amps from 12V FLA batteries... a total act of atrocity, an invitation to kill bateries very quickly. From Netgain shop manual:
> 
> "... 12 Volt PbA batteries would sag to 5.5 Volts when 1,400 Amps were drawn from them. If the motors are capable of handling 168 Volts, and the PbA battery pack is 168 Volts nominal, then the motor would only see about 77 Volts when 1,400a was drawn from the battery pack. In order to deliver the maximum voltage to the motor, it became necessary increase the PbA battery pack voltage."


OK be careful here because you are drawing the wrong conclusion. That is leading you to the false conclusion that the problem is limited to Pb batteries which is false. In fact Pb batteries actually have excellent Voltage Sag characteristics. Lithium Ion batteries have higher voltage losses because they have lower Specific Power densities than Pb. in other words higher Internal Resistance on a AH per AH basis. W/Liter and W/Kg

Where Lithium holds the advantagein DIY and commercial EV's is Energy Density Wh/Kg and Wh/L



ekthor said:


> Is it really possible to get so much amperage from a 12V PbA battery? Isn't that limited by the battery internal resistance?


Absolutely Yes. When you buy a SLI battery aka Starting Lighting & Ignition they have what is called PHCA, HCA, CCA and MCA. On a 12 volt battery Cranking Amps is specified at some temperature at 7.2 volts. That is directly proportional to Internal Resistance. Take an _*Odyssey PC2250*_ a 12 volt 120 AH battery, has an Ri 0f .0025 Ohms. PHCA is how many amps a battery can deliver at room temp for 5 seconds and the PC2250 can deliver 2250 amps. Odyssey batteries are AGM Pb batteries and AGM batteries have extremely low Ri and used by drag racers because there is no better battery with one exception. A RC Hobby LiPo battery can match it and do better with LESS Weight. But RC LiPo's are extremely dangerous and unstable not to mention unbelievable expense with very limited cycle life. Only E-Bikers use them in an EV. To dangerous. 

Food for thought. Plum Quick, the worlds certified fastest golf cart holds the record at a 118.76 mph, 12.24 second quarter mile. Of course they used their Series Wound DC Motors and Odyssey PC2250 AGM battery. Look for yourself.


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## john61ct (Feb 25, 2017)

What about the Alber Cellcorder? I have a chance to pick one up very cheap?



Sunking said:


> That is leading you to the false conclusion that the problem is limited to Pb batteries which is false. In fact Pb batteries actually have excellent Voltage Sag characteristics. Lithium Ion batteries have higher voltage losses because they have lower Specific Power densities than Pb. in other words higher Internal Resistance on a AH per AH basis. W/Liter and W/Kg


Are you speaking of LiFePO4 specifically or all Li chemistries?


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## Sunking (Aug 10, 2009)

john61ct said:


> What about the Alber Cellcorder? I have a chance to pick one up very cheap?


I have quite a bit of Alber equipment, most of it for sale. 

I do not own a Cellcorder, I think they are discontinuing, not sure. Does not really matter any Ri or Conductance meters are good. The trick to any of them is to establish a Baseline when the batteries are new and keep a log book. You can spot a problem real fast and take corrective action if possible. So if you can get it cheap go for it. An up to date Midtronics model is $5500. 




john61ct said:


> Are you speaking of LiFePO4 specifically or all Li chemistries?


Pretty much all of them with the exception of Hobby RC LiPo's. LFP of what you call LiFeP04 is decent, better than most of the other lithium types like NCO, NMC. Really in a DIY EV LFP is the way to go because they have about the lowest Ri aka highest Specific Power Density of the lithiums. Commercial Ev's don't use them because they run much higher voltages, so they do not really need 5C for acceleration, or 1C for cruising. If you stop and think about it an EV with a 200 mile range is cruising at C/3 to C/4 rates. A 300 mile Tesla at C/6. 

With a DIY EV running 144 volts and lower, you got no choice but to run very high discharge rates. 

Almost forgot LTO or Lithium Titanate has excellent Specific Power, but two killers; Low Energy Density equal to PB, and a price tag that make it impossible to use on a EV. A Chi-Com LFP like Calb runs you around 50-cents per Watt Hour, an LTO around $5 per watt hours and weighs a ton. However for a solar system maybe doable in a commercial system because LTO cycle life on paper is 10,000 cycles with 99.99% charge efficiency.


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## Sunking (Aug 10, 2009)

ekthor said:


> *** Now a personal question for my EV, a classic VW beetle. As I said, I'm using the AMD 9" motor, single shaft, and the Kelly Controller KDHE 144V600A (its Voltage limit is 180V). My PbA batteries are new, 1 month old, some 7 cycles only.
> 
> I reviewed Trojan Manual to see what the full charge voltage I could get with 14 batteries at 100% SOC, I found 12.73 x 14 = 178.22. Almost 2Volts from the overvoltage limit, and because this is DC motor without regen, I believe that was the perfect configuration. Wrong.
> 
> Some 8 to 10 hours after charging, the voltage is around 184.3V, impossible to use the EV, I let the pack rest some 8 hours more... 183V, the voltage does not decrease as fast as LiFePO4 cells. After almost 20 hours the voltage does not go below 182V = 13V!! way above the 12.73 trojan states as 100%SOC


Ektor you are making the same mistake billhoc is making. Using voltage to determine SOC on a Pb battery is useless. Voltage as SOC indicator is only usable on a fully rested battery of 12 to 24 hours. Even then is only a Ball Park indicator. Bill did not want to hear this but maybe you will listen. There is only 1 way to determine a FLA SOC in real time, a Temperature Corrected Battery Hydrometer for $10 or less. _*Best $7 investment*_ you'll ever make. FWIW a low Specific Gravity = Under Charged battery, a recipe for short battery life. They must be kept fully charged at all times, and immediately recharged after any use. Charge at every opportunity. If you have 14 x 12 volt Trojan batteries, they must be charged to 14 x 14.43 volts = 202 volts if you use Fast charging aka Daily Charge.

Perhaps this might help. You have fallen into a 3 Stage Charging Algorithm, which is marketing hype. It is stressful to Pb batteries and not necessary. Utilities would never ever use 3-Stage charging. Shortens battery life. There is another way to fully charge Pb Batteries and it is called FLOAT CHARGING. The down side and why it is not used much for daily users is it takes longer. Up to 24 hours if you discharge more than 50%. Trojan Specifies FLOAT CHARGE voltage of 2.25 vps or 13.5 volts on a 12 volt jar. You would use a simple CC/CV charger set to 14 x 13.5 volts = 189 volts. As with any Pb battery you want to charge no less than C/10 and no faster than C/6. Still too high a voltage for your controller, but an option. Sounds like you need to loose 2 batteries. Perhaps you have a boat in need of an anchor, trolling motor, or fish locator. Or how about two of them in parallel for your 12 volt systems in your EV? Think outside the box.


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## john61ct (Feb 25, 2017)

Sunking said:


> As with any Pb battery you want to charge no less than C/10 and no faster than C/6.


That's just nuts. True most FLA won't actually accept higher than .2C, but it does no harm with any lead for the charge source to offer high amps, even 4-5C, process is self-limiting. Even a 320A alt on a single starter batt, of which there are millions on the road.

Assuming temp sensing and sound wiring infrastructure of course, against general heat/fire risks. That's really the only reason many mfg CYA legally with a max charge rate spec.

Most quality AGM now want to see .2+C; Odyssey's is .4C as a bare **minimum** for longevity, or 40AH of current per 100AH storage.

Lower rate sources like most solar, or float charging, will greatly reduce bank longevity.

Of course EV use, as discussed above, makes longevity pretty much a moot point anyway. But for those who want to minimize charging times during the Bulk and early Absorb, say up to 75-85% SoC, there's no such thing as offering a lead bank "too many" amps, it will self-regulate via its CAR/resistance.


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## Sunking (Aug 10, 2009)

john61ct said:


> That's just nuts. True most FLA won't actually accept higher than .2C, but it does no harm with any lead for the charge source to offer high amps, even 4-5C, process is self-limiting. Even a 320A alt on a single starter batt, of which there are millions on the road.
> 
> Assuming temp sensing and sound wiring infrastructure of course, against general heat/fire risks. That's really the only reason many mfg CYA legally with a max charge rate spec.
> 
> ...


No now you are talking nuts and you cannot compare FLA to AGM. Read any quality manufacture like Trojan or Rolls FLA is C/10 to to C/6 ak .1 to .15C is recommended. Any slower than C/12 and you risk Stratification, To fast and you will cause excessive gassing and plate corrosion. AGM is different, Optima, Odyssey, and the cadillac of AGM batteries Concord reccomend C/4 to C/2. 

Besides for a EV I would like to see a 144 volt charger than can do anything higher than C/6. On a 225 AH amp battery is 40 amps, and at 144 volt nominal would require a 8000 watt charger operating on a 240 VAC 40 amp circuit. C/10 on a 144 volt battery is about the limit for most homes and that requires a dedicated 120 volt 20 amp circuit. 

For solar requires at least C/10 to C/6 to replace what is used in a day. I have over 300 commercial Off-Grid Solar systems designed, built and in operation to date and counting of 2000 to 5000 watts At 48 volt battery with capacities up to 1000 AH.

For Telecom plants we use special Stationary Batteries using up to 40,000 AH batteries with 16,000 amp rectifiers operating at 48 volts. Verizon who I work for is the worlds largest battery customer,, and I design and build the battery plants. I sit on IEEE Battery Standards Committee for 25 years working with all major manufactures. We write the practices.


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## john61ct (Feb 25, 2017)

None of which contradicts what I wrote. My point is simply that, as long as voltage is kept within spec and temp controls are in place, no lead bank will accept enough current to cause itself any harm, the charge source is simply offering Amps, the bank's CAR/resistance is what is controlling the actual current flow.


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## Sunking (Aug 10, 2009)

ekthor said:


> Hello SunKing and all,
> 
> OK, I will use a new T.C.B. Hydrometer to measure specific gravity. While it arrives… would you say the batteries were “overcharged”, they have been idle for more than 24 hours and they are above the referenced, ball parked 100% of 12.73V, around 12.9v average each.


I have doubts you are over charged and thus why I do not like or trust SOC monitors. A hydrometer is going to tell you what is really going on inside. In fact I think you are UNDER CHARGING. Keep reading. 



ekthor said:


> I’m using a 2 phase, 220VAC simple capacitive battery charger for them, it charges first at 13.6A until I get 183.3V (90% or Trojan’s “Absorption Charge”) then in 2nd phase 3.5A, up to 192.4V.


FWIW that is Single Phase. Really makes no difference what it is. 



ekthor said:


> Trojan mentions 5 different charging voltage settings in its manual, and says no further info about them.


Manual is a bit outdated. Not sure that model you have just guessing and going in you said 12 volts something like a T1275. Does not matter what model it is, all I need to know is it is FLA. Otherwise a Hydrometer is useless. 

If you look at the actual Spec Sheet they list 3 voltages. 

Bulk = 14.83
Float = 13.5
Equalize = 16.2

Bulk is used for daily chargers and is referred Daily Charge/ It gets confusing because you hear so many terms out there. like Bulk, Absorb, Float, Daily, Equalize, and the list goes on. You are looking to charge at 14 x 14.83 = *207.62* volts until Charge Current tapers down to .03C. _So what voltage did you say you are charging at? _

Once current tapers to .03C. lower the voltage to 14 x 13.5 = 189 volts which is called Float and leave it at 189 volts until the end of time and you die. 

The third voltage is Equalize which is sometimes called Boost or Maintenance charge. On average this is done once a month. In practice you only do this WHEN NEEDED. How do you know when it is needed? Your battery hydrometer will tell you. After a full charge, you measure the Specific Gravity of each cell. If there is a spread of more than .030, it is time to EQ. So 14 x 16.2 volts = *229 volts*. 

_So what voltage did you say you are charging at? _

EQ can take up to 24 hours. You keep applying EQ until the specific gravity quits rising for 3 hours. 

Here is what Trojan says in FAQ.



> 1. When do I need to perform an equalization charge?
> Equalizing should be performed when a battery is first purchased (called a freshening charge) and on a regular basis as needed. How often this might occur with your battery will vary depending on your application. You will need to monitor your battery voltage and specific gravity to determine when equalization is needed. For example, it is time to equalize if the measured specific gravity values are below manufacturer’s recommended values after charging (recommended value for Trojan Deep Cycle batteries is 1.285 +/- .007 at 80º F (27º C)). Equalizing is also required if the specific gravity value of any individual cell varies 30 points or more. In addition, reduced performance can also be an indicator that equalizing is necessary. Equalization should be performed when individual battery voltages in a battery pack range greater than 0.15 volts for 6-volt batteries or 0.30 volts for 12-volt batteries.


Now here is the exact EQ procedure from Trojan.



> FLOODED BATTERIES ONLY
> 
> Equalizing is an overcharge performed on flooded lead acid batteries after they have been fully charged.
> 
> ...


_*
Have you ever performed an EQ charge at ? *_ Bottom line is get your Hydrometer out and see what is really going on. Me thinks you are a Chronic Under Charger.


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## john61ct (Feb 25, 2017)

ekthor said:


> would you say the batteries were “overcharged”? they have been idle for more than 24 hours and they are above the referenced, ball parked 100% of 12.73V, around 12.9v average each.


Again, **voltage is not a reliable indicator of SoC**, unless rested 24+ hours and compared to benchmarks previously set for that specific model of battery.

IF your bank is healthy, then a "declining current setpoint" like this:



Sunking said:


> You are looking to charge at 14 x 14.83 = *207.62* volts until Charge Current tapers down to .03C


is the best way to define "full".

SG reading with a hydrometer is more convenient than voltage, since no resting period, but still not as accurate as the above, or at least varies by battery model.

You need to get the SG to SoC chart from your manufacturer. 

Avoid buying batteries made by companies who can’t provide this sort of detailed information.


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## john61ct (Feb 25, 2017)

ekthor said:


> So, once again it is: 183.3V for first phase at 13.6A, then 3.5A up to 192.4V. According to Trojan's charging chart, voltage keeps raising 'till the end of charge.


No. 

Voltage hitting your setpoint is just the end of Bulk and start of Absorb, maybe 70% SoC, many many hours from 100% full, depending on the charge current vs bank size.

You really need to measure the current and keep pumping Absorb voltage until Amps drops to a tiny fraction of the AH C capacity.

Once you have gotten familiar with your patterns, you may find say 3.5 hours is enough from 50% SoC, but 6 hours is needed when DoD is 80%.

But ideally for longevity, you're using the dropping amps setpoint, or calibrated SG from hydrometer every time.


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## Sunking (Aug 10, 2009)

ekthor said:


> The numbers are for 13 FLA batteries, not 14 SunKing.


OK my bad. Then you only need to know 1 voltage. 13 x 14.83 = *192.8 volts. *



ekthor said:


> So, once again it is: 183.3V for first phase at 13.6A, then 3.5A up to 192.4V. According to Trojan's charging chart, voltage keeps raising 'till the end of charge.


Let's see is this helps. You are still getting confused with Terms. 

Bulk = Constant Current Mode
Absorb = Constant Voltage

Both are really BS terms. In simple terms you want a charger CC/CV charger you can set voltage.

Daily Charge = 192.8 volts and that CC/CV aka Bulk/Abosrob. You terminate the charge when Charge Current tapes to .03C. It is not a Voltage Event, it is a Current Event. 

All chargers do the exact same thing and are all CC/CV. Just some have more Bells and Whistles with catch Marketing names like Smart, 3-Stage, 4-Stage, and the list goes on. The simplest charger is just a DC Power Supply with a current limiter. 

Example let's use some realistic numbers you can relate to. Assume we have 13 of your batteries, and you have a 15 amp charger. Batteries are at 50% SOC and resting at 157 volts. Batteries are in good condition with an Internal Resistance of .006 Ohms per battery x 13 batteries = .078 Ohms total Ri. With me so far?

We set our DC power supply aka charger to 193 volts. The charger can only output 15 amps, and we connect it to the batteries. Again the OCV of the batteries is 157 volts. The voltage of a *Charging Battery = OCV + (Ri x Charge Current).*

The moment you connect the charger the charger voltage is going to fold back 157 volts + (.078 Ohms x 15 amp current limit) = *158 volts*. The charger will keep supplying 15 amps. This is the *Constant Current Mode* aka BULK.

As the battery charges up with a *Constant Current*, the voltage will rise, and continue to rise until voltage reaches 192 volts. At that moment magic happens called the *Constant Voltage Mode* aka ABSORB. That is when charge current will start to taper down falling from 15 amps. At this point your battery is roughly 90% SOC. As the voltage continues to rise from 192 volts and approaches 193 volts, current will Taper Down and you terminate the charge when the current reaches .03C. that can take anouther 2 to 6 hours. So if your battery is say 150 AH would be 4.5 Amps. Terminate charge. 

Now is 193 volts the right voltage. Well in Spring and Fall it might be, who knows. But I can tel you it will be higher than you are using today. So how do you know what the exact voltage is? That is why you just spent $7 on a Hydrometer. After a full charge cycle, measure the Specific Gravity. If SG is low, turn up the voltage. If SG is to high,, lower the voltage. What you will find is in Winter Months you have to raise the voltage, and lower it in Summer. 

About once or month or so you will notice SG becomes unequal. That means it is time for a EQ charge at 13 x 16.2 volts = 211 volts.

EDIT NOTE. 

Notice how the battery Internal Resistance comes into play while charging? Exact opposite of Voltage Sag while discharging.


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## Sunking (Aug 10, 2009)

john61ct said:


> None of which contradicts what I wrote. My point is simply that, as long as voltage is kept within spec and temp controls are in place, no lead bank will accept enough current to cause itself any harm, the charge source is simply offering Amps, the bank's CAR/resistance is what is controlling the actual current flow.


Wrong John. You are right a battery is self limiting via its *Internal Resistance.* But you definitely do not want to charge to fast or you will gas the crap out of the electrolyte and corrode the plates. 

Lets say I have a charger with unlimited AMPs of charge current. Now lets say I have a 12 volt 100 AH battery with .01 internal resistance and the battery is 50% SOC with a resting voltage of 12.1 volts. A good healthy Trojan battery. So I set the charger to 14.83 volts as Trojan recommends Daily Fast Charge and connect the battery. 

Instantly as soon as I connect the charger there will be 14.83 - 12.1 volts / .010 ohms 273 amps of charge current. Let's ignore the fact the Term Post would likely melt and the Plates would warp. Current would not taper until the battery reaches 60 to 70% SOC. As soon as you connect the charger you are in Gassing Voltage and Corroding the plates. That occurs at roughly 2.4 volts per cell or 14.4 volts. Not to mention Boiling the batteries hard with Electrolyte spewing out which cannot be replaced. 

That is why manufacture limit maximum charge rates to about C/6 to C/8. So when you stay below Gassing Voltage for as long as possible. C/10 is perfect. When you reach 14.4 volts at the slower rate, your SOC is around 90%, and thus does not stay at or above gassing voltage for as long is you charge faster. 

As I said earlier using a fast charge method above 2.4 vpc is hard on batteries. It shortens battery life from corrosion and makes them use more water from electrolizing aka gassing. This is exactly why utilities only use Float Chargers set to 2.25 vpcs for FLA batteries, and 2.35 vpc for VRLA aka AGM. A good Pure Lead Station Battery will get 30 to 50 years service life with 20 year warranty periods.


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## john61ct (Feb 25, 2017)

300+ amps is an entirely normal charge current to apply to any reasonably sized 12 V bank. No lead melting I promise.

Yes faster transition to CV that's the whole point, minimize yacht engine runtime, maybe 40 min. all up to 75-80%, then finish the long tail with a day of solar.

Try it sometime when you get a chance, and you'll see, theory doesn't match reality.


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## john61ct (Feb 25, 2017)

Sunking said:


> John I will give you a tip every Utility, Telephone, and Cell Phone Tower operator uses to benchmark batteries. Even DIY can do it. All it takes is a few minutes.
> 
> Measure your battery Ri when new after few cycles. Makes no difference if they are Pb or LFP. You can use your motor controller shunt and a volt meter as I already described. Only takes a few minutes. There is a direct correlation between Ri and Capacity.


Apparently not

https://marinehowto.com/are-battery-conductance-testers-worth-it/

http://www.trawlerforum.com/forums/showthread.php?p=568240


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## john61ct (Feb 25, 2017)

Perhaps in measuring remaining capacity and State of Health, the high-current-discharge EV world corresponds more closely to CCA measurement, than it does in solar/RV/marine House bank usage.

I will for now stick to standard 20-hour discharge tests, may be tedious, but I like cheap and accurate.


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