# Batteries losing charge too quickly?



## Woodsmith (Jun 5, 2008)

At Arch's (my partner) works they have a 48V Bradshaw FB2 (called Beryl) for collecting recycling around the York City centre.

On a full charge Arch can get Beryl around half the round before unloading and topping up the charge for an hour over lunch for the second half of the round.

Today Beryl had a brake replacement and service in the morning, prior to starting its round, that took from 8am to 11am during which time the charger had been unplugged.
Beryl only managed about 2 miles and had to be unloaded and coaxed back to base.

Any reasons you can think of as to why it should lose so much charge?

I am wondering if something is discharging the pack or if it is just down to useless batteries. I will be over there on Friday and was wondering if there is anything I can easily check?

The pack is made up of 8 x 6V lead acid cells.

Cheers.


----------



## piotrsko (Dec 9, 2007)

I'd suspect poor workmanship on the brakes first, something might be dragging. Secondly look to ambient temps, thirdly look for transients on the batteries. for a week's time I would think you have better than 300 ma leak going on. For 4 hours it would have to be about 10-20 amps like leaving on the headlamps.


----------



## Woodsmith (Jun 5, 2008)

Well, the brakes have been serviced now so there _should_ be no problem there. It does roll ok.
The ambient temp has been hovering around 0C-5C overnight and it is stored in a shipping container with an overnight heater left on. The charger has recently been put on a timer to ensure that it gets to full charge just before use in the morning and that has made sure that it was able to do its rounds this winter.

I will try to check for current flow when it is static and also see what the battery voltages are like at the end of its working day.

Bradshaw's battery maintenance schedule seems to be a case of swapping out individual dead cells once in a while. I reckon all the cells are of different ages and with different numbers of charge cycles.
It wouldn't surprise me to find a dead cell. I will see tomorrow when I am over there.


----------



## Woodsmith (Jun 5, 2008)

I've got some readings from the pack and my phone just lost the long post I just made!

Anyway, I get here after lunch and she had just had a 1.5hour top up charge and was reading full.
These are the pack and cell voltages before and after a 2 mile round.
53.4v 51.0v

6.6 6.3
6.7 6.5
6.7 6.3
6.7 6.3
6.8 6.4
6.7 6.3
6.6 6.3
6.8 6.5

There seemed to be no current drain when off, negligable current when on, about 10-20A with lights etc on. I had a quick ride in the back unladen and recorded around 50-70A running with starting peak just over 100A. That was just off scale on one meter and too small on the other meter.

I will try to get another test done on a properly long collection round.


----------



## poprock (Apr 29, 2010)

Hi Woody. re battery readings.By my limited experience they're ok. My Trojans and Century 6v 105's ( yes , mixed in a pack ) show the same figures on average. A crookie will read approx 6.2 charged and then will drop to under 6 after a run.Then it's off to the scrap yard. Incidentally, my batteries come from an aluminium smelter and are always replaced by them as a complete pack, as you suggested. Generally there are are only 2 or three out of a 12 pack which are bad.


----------



## Woodsmith (Jun 5, 2008)

Just found I have missed taking readings as Beryl had to be pushed back! She is back on charge now having done less then 3 miles.

The usual round on Monday, and most days, is only about 6 miles now with a mid day recharge. 
Not good.

Beryl only weighs 630kg with a load up to 550kg.
Batteries are 8 cells, 48v, 175Ah.


----------



## Woodsmith (Jun 5, 2008)

Also thinking about converting to lithium with a 72v, 200Ah pack now.

The current three miles on a charge seems silly.


----------



## Guest (Jan 23, 2012)

Woodsmith said:


> Also thinking about converting to lithium with a 72v, 200Ah pack now.
> 
> The current three miles on a charge seems silly.


By all means upgrade to lithium. The issue is quite common with the lead acid cells and it really just plain sucks. Get the lithium and be a real happy camper. Get some good AH cells so you can drive the whole day without having to recharge. Really. Lithium will make life much easier. No more muss and fuss with the heavy lead acid cells and no more filling and checking. Put them in and get a charger that will not over charge them. Make sure you bottom balance them and then don't drive them to the ground. 160AH cells should do you just fine. Vehicle will be much lighter too.


----------



## Guest (Jan 23, 2012)

Woodsmith said:


> The current three miles on a charge seems silly.


More like insanely ridiculous to carry around a heavy lead acid pack to go only three miles.


----------



## Woodsmith (Jun 5, 2008)

gottdi said:


> More like insanely ridiculous to carry around a heavy lead acid pack to go only three miles.


They are thinking of a replacement vehicle but are struggling to find a suitable off the shelf vehicle so I suggested considering upgrading Beryl to run better.


Right, could someone check my maths on this please?

I put some figures into my spreadsheet to emulate a very bad Beryl. That required giving her the aerodynamics of a house brick flying a flag and rubbish tyres rolling on grass at 20 mph. That made her replicate the current readings I took so I will go with that as being good enough that she draws, say, 65 Amps running.

So, with a pack capacity of 175Ah and her motor drawing 65A Beryl could run for 2.7 hours.
At 20mph that means she would cover 54 miles.
With 50%DoD she should be good for 27 miles.

As a ball park she should do a lot better then 3 miles per charge.
Even if Beryl was drawing twice the current, with a head wind and a heavy load, she should still be good for better then 10 miles per charge or are we missing something?


----------



## Woodsmith (Jun 5, 2008)

I have received a set of readings from Beryl's batteries, taken over the course of yesterday.
The readings were taken (A) prior to setting out in the morning with an 8 hour charge, (B) on return after 3.8 miles, (C) after a 2 hour lunchtime charge, (D) on return after 3.8 miles at the end of the day.

A---B---C--D
6.6 6.2 6.6 6.3 New Aug 2011

6.8 6.5 6.7 6.4

6.7 5.6 6.7 5.7

6.6 5.7 6.6 6.3

6.7 6.4 6.7 6.5 New Aug 2011

6.7 5.6 6.7 6.4

6.6 6.3 6.7 6.2 New Aug 2011

6.7 6.5 6.8 6.4

The whole pack was renewed by Bradshaws in July 2009 for the second time since 2006 and three batteries replaced last August.

Three of the current batteries have dropped below 6 volts after the morning run. 
The Curtis battery meter had just gone into the amber on each return.

Could the three batteries that sag below 6V be the problem?
Also could the constant stop start of door to door collection also be a problem?

Beryl, we think, has some kind of regen. Not sure if she really does or if it is plug braking, she has a DC Sevcon controller, I'll check what sort later.

The ideal need is for Beryl to be able to cover 15-20 miles per day on one charge, carry a full load and tow a trailer.
She weighs 650kg unladen but with batteries, will carry up to 1000kg and ideally tow about a 750kg laden trailer.

Any advice on lithium would be good or any advice on how to get the most out of her on lead for the time being also much appreciated.

Thank you.

This is Beryl.


----------



## poprock (Apr 29, 2010)

poprock1 said:


> Hi Woody. re battery readings.By my limited experience they're ok. My Trojans and Century 6v 105's ( yes , mixed in a pack ) show the same figures on average. A crookie will read approx 6.2 charged and then will drop to under 6 after a run.Then it's off to the scrap yard. Incidentally, my batteries come from an aluminium smelter and are always replaced by them as a complete pack, as you suggested. Generally there are are only 2 or three out of a 12 pack which are bad.


Replace the three under 6 or  blow the budget and replace the lot for the sake of Beryl's future happiness.


----------



## piotrsko (Dec 9, 2007)

^+1 I'd do the whole pack, especially if I could find a rebuilder and get them redone to my specs. Sounds like you are going to have to replace the pack eventually and I, as yet, do not see lithium chemistries being cheaper for the next 2 years or so. The other option would be flooded NICADs, but then you have the whole charger issue to deal with in addition.


----------



## Guest (Jan 28, 2012)

> and I, as yet, do not see lithium chemistries being cheaper for the next 2 years or so.


True, but what you will/are seeing, is more power and density for the same pricing you are currently getting. So you will get more for your money. Don't forget to crunch the numbers. Just because the pricing is high up front does not make them more expensive than lead, nicad, NiMH or Nickel Iron batteries. Lithium is the way to go. Pricing is overall cheaper for the life of the battery than even the cheap lead acid cells.


----------



## Woodsmith (Jun 5, 2008)

gottdi said:


> True, but what you will/are seeing, is more power and density for the same pricing you are currently getting. So you will get more for your money. Don't forget to crunch the numbers. Just because the pricing is high up front does not make them more expensive than lead, nicad, NiMH or Nickel Iron batteries. Lithium is the way to go. Pricing is overall cheaper for the life of the battery than even the cheap lead acid cells.


This is sort of what I was assuming.

I've not got UK dealer prices but using ball park figures a new pack of the same overall capacity would cost a fair bit more but we may be able to get more out of a good, but smaller lithium pack for not much more money.

I have to work out the differences between just putting in a 48V lithium pack and going up to 72 volts with the change in controller, charger, DC-DC and other miscellaneous parts.

Reading the generic mantenace manual it seems to suggest that the current set up uses a Sevcom controller and the motor is a sepex but it gives no details.
Also it says the 12V supply is a battery tap off but looking at the back connections there is only a tap off at 48V so there might be a DC-DC installed somewhere.

The user instructions suggest some sort of plug braking as it goes through a test procedure for measuring field current when Beryl is pushed and says that rolling resistance should increase rapidly until she can't be pushed any further.

I can't see anything obvious regarding regen though, yet.

Another option would be to replace some/all the batteries like for like for now and start working on an in house construction of a whole new vehicle from scratch for lack of manufactured alternatives.


----------



## bgeery (Oct 17, 2011)

A lithium conversion make even more sense for businesses. You have to pay people to maintain the cells vs a DIY hobbyist, and lithium is a lot less work to take care of. Just make sure you don't have any sub-taps off the pack and bottom balance the pack to be safe.


----------



## piotrsko (Dec 9, 2007)

gottdi said:


> True, but what you will/are seeing, is more power and density for the same pricing you are currently getting. So you will get more for your money. Don't forget to crunch the numbers. Just because the pricing is high up front does not make them more expensive than lead, nicad, NiMH or Nickel Iron batteries. Lithium is the way to go. Pricing is overall cheaper for the life of the battery than even the cheap lead acid cells.


Did crunch the numbers and yes for the exorbitant price up front I can do that. Notice I said price up front. This is a Huge Big deal when the funds aren't there. Perhaps you will front me the money for a 300 V 30 KWH pack that I can pay back in 3 to 5 years? The banks I frequent won't.


----------



## Woodsmith (Jun 5, 2008)

I think if it came to it, and a good case can be made, we may be able to free up funds for Beryl's battery pack to be completely replaced. However, that will need a full and fairly accurate investigation and report to justify it and I would need to be really sure that the pack is properly suitable and will do what is required without being over sized and over priced. I would also need to make sure I include other ncessary components like BMS and maybe even a replacement charger if the existing one isn't good for lithium.


----------



## Woodsmith (Jun 5, 2008)

Is there an easy (cheap and simple) method to monitor the current drain form the pack over the course of a day?

I was just wondering about how much of the energy is used for all the restarts under load and how much would be just steady driving given the nature of stop start door to door collections.

I can rig up a multimeter to read voltage so the driver can monitor sag but current draw would be a bit more difficult as would noting the readings while driving and doing a job.

I know nothing about, and have never used, a data logger of any sort.

Cheers.


----------



## piotrsko (Dec 9, 2007)

Here in the US one can rent devices for electronic testing purposes. What they do is accept a voltage/current/frequency, convert it to digital and with software write it to a file on a PC. Many input channels, usually a serial or USB port for about $35-50 USD a month. Here they are listed under Test Equipment rental in the Thomas register which I believe you have an equivalent to ( or otherwise google)


----------



## Woodsmith (Jun 5, 2008)

I will have a look around to see what is available here, cheers.

They do have a student doing research there at the moment ahd he has data loggers all over the place taking temperature readings. Maybe I need to see what he is doing too and pick his brains.


----------



## Woodsmith (Jun 5, 2008)

OK, an Update on Beryl.

Following an examination she is looking a rather rusty underneath and management are doubtful she will structurally last as long as a lithium pack.

So she has been treated to a new pack of 205Ah lead.
She is currently running at 8 miles a day without a lunchtime top up charge though I haven't had a chance to get any more battery readings from her.

The plan is that the new pack will buy us a year to find a replacement vehicle. That is proving to be the difficult part.


----------

