# 80 Volt Battery System and Charger?



## tomsbradford (Nov 8, 2013)

What do you think about an 80 volt lead acid battery system? As I explained in another post ("First EV, First Post"), I bought a Bug with the ALLTRAX 7245 and dead batteries. I understand that this controller can handle 90V. I'm a little reluctant to push it that far and am considering ten 8V batteries. The trouble is, several searches have only uncovered one charger in China that is $550. Don't know how smart it is. Suggestions?


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## frodus (Apr 12, 2008)

Stick with 72V, or get a higher voltage controller (Curtis 1221/1231).

It will be pretty difficult to find a charger to go to 90V and not over. Those Ten 8V batteries will need to charge to about ~9.8V, so 98V for the pack. The Alltrax either won't start, or you'll damage it.


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## poprock (Apr 29, 2010)

As per a previous post, I am using the Alltrax 7245 with 7x12v. When charging 93 volts can be showing; when disconnected the batteries drop to around 91v. My el cheapo brand voltmeter tells me the 7245 kicks in when 90.2 v is reached. Damage is unlikely because this is the maximum voltage programmable by factory settings.


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## frodus (Apr 12, 2008)

Actually, anything over the programmed max (90V) could damage the controller. It doesn't turn on the output if the voltage is higher than that, but what we don't know, is what voltage will damage the controller above 90V. Could it be 120V? Yeah. But it could also be 100V, depending on how they chose the components inside.

At some point, the voltage going into the controller will damage the components inside the controller. To say damage is unlikely is misleading..... 92-93V or so may nod damage it, but more may.


To the OP, read this:
http://www.diyelectriccar.com/forums/showthread.php/90v-alltrax-7245i-37590.html


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## tomsbradford (Nov 8, 2013)

I appreciate your cautions frodus, and your reported experience poprock1. That's good information and will help me with my decision. But for discussion sake, if I do go with an 80 volt system, should I figure on a 72V charger on nine batteries and an 8V charger on the tenth battery?


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## rmay635703 (Oct 23, 2008)

tomsbradford said:


> I appreciate your cautions frodus, and your reported experience poprock1. That's good information and will help me with my decision. But for discussion sake, if I do go with an 80 volt system, should I figure on a 72V charger on nine batteries and an 8V charger on the tenth battery?


NO, do not mix different batteries!

Those of us who scrimpt off a junkyard will play with random batteries but understand that you will always be overdischarging the 12v batteries or just not exercising the 8v battery much. Mixed batteries will mean constant maintenance and monitoring, if you want that get lithium.

best to have all batteries the same voltage, 8v are MUCH better than 12v in FLA and last about 50% longer lifespan.

So if you want to mix chargers charge the 9x8v on the big 72v charger and one 8v charger off the tap.

Lead is so simple to charge you could also just use a constant current charger and kill it after a voltage or timer is met or buy something like a K&W BC-10 which supports 80volts natively anyway.

Good Luck


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## rmay635703 (Oct 23, 2008)

tomsbradford said:


> What do you think about an 80 volt lead acid battery system? As I explained in another post ("First EV, First Post"), I bought a Bug with the ALLTRAX 7245 and dead batteries. I understand that this controller can handle 90V. /QUOTE]
> 
> I have been running a Curtis 1204 48v controller at 60 volts for years without any detectable ill affect, some controllersare overbuilt, others not so much, I would question the reliability of the alltrax at anything other than 72v but its only par for the coarse.
> 
> Do it and report back if it breaks.


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## tomsbradford (Nov 8, 2013)

Thanks. I'll report any results.


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## poprock (Apr 29, 2010)

In your other thread Black Panther posted in april 09 that it would be wise to disconnect the pack, including precharge resistor when charging. Whilst no immediate damage may occur it could reduce overall life . Or as Renny suggested, copy the Zap pk system which removes one battery from the system until voltage drops under 90v. I will err on the side of caution


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## onegreenev (May 18, 2012)

Stick with 6v or 8v or 12v batteries and don't over volt your controller. Even those that over volt the AC Curtis controllers are playing with trouble. Use the proper charger. 72 volt charger for a 72 volt nominal system, Same for 96 volts or 120 or 144 or 156 or 192. If you want it to last use it within the parameters designed.


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## tomsbradford (Nov 8, 2013)

Because the speed limit is 45 and hilly on my planned ten mile round trip commute, I am now leaning toward a 96V system. What's the best way to sell the 72V motor and controller and buy/upgrade to a 96V system? I assume nothing else needs to change (other than more batteries).


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## rmay635703 (Oct 23, 2008)

9 times out of 10 a 72v motor will run on 96 volts without issue, especially if it is a 72v forklift or industrial motor, if its one you bought from an "ev place" then I would ask Major or someone else here familiar with motors to get their opinion on your particular model.

Generally even an undersized motor can be run at higher voltages so long as you limit amps to a reasonable amount and advance brushes a tad (if needed)

Your only thing that would need to go would be the controller.

If I were you I would figure out what controller I want, determine what I need to do so I can easily swap the controller later.

AND MOST IMPORTANTLY USE WHAT I ALREADY PURCHASED.

Then camp out to get the best deal on the type of controller I want and enjoy my ev at lower speeds until I do, you can then get bugs worked out and ENJOY the upgrade even more at a later date.

To boot you likely won't get much less cash for your used controller as you would new. Same goes for the rest, no sense tossing it out when most of it will work fine on 96v.

Also there are chargers out there that are cheap and easy to reconfigure to various voltages, including ones you build, so the charger will be a non-issue.

Keep contactors run off your 12v system and then there are no worries when it comes time to upgrade to 96v.

Good Luck
Ryan


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## tomsbradford (Nov 8, 2013)

Sound advise. Thanks! BTW. The ES-15A Series Motor and Alltrax 7245 controller came with the beetle.


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## tomsbradford (Nov 8, 2013)

Okay, reporting back. finally got the batteries in - 80V. It seems to function fine, considering I am operating at higher than manufacturer's specification. Time will tell if I pushed it too far - not as far as those reporting operating at 84V.

I can charge at 72V now. Planning on buying an 8V charger for the last battery.


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## tomsbradford (Nov 8, 2013)

Update. Could use some advice too, please:
Did a little research and read where others operated this kit at 84V. I was nervous about driving the equipment so far above the 72V specs and decided to compromise at 80V (ten 8V 165AH batteries). The terrain is rolling hills with one stop sign on the way to the train station. Elevation increases by 275 feet from the train station to my house, so it is mainly coasting to the train station and working hard to get home. I drove the little bug around for a couple of months. On the way home the Bug would slow to about 30 MPH going up the main hill and the motor would get hot - too hot to touch. Last week the motor died just a few yards from the house. I have yet to do an autopsy.
I think I need to upgrade voltage to 96V to get a little more speed to get closer to the 45 MPH speed limit. That’s a convenient voltage, in that I can just add two more 8V batteries. I also may need to force cool the motor. What motor and controller would you recommend to minimize cost and re-conversion work? Used equipment is OK with me. What additional components would I need to upgrade?


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