VRLA equalizing charge: series connected

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randalson
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VRLA equalizing charge: series connected

I have a scooter with 5 12V VRLA batts in series for 60V. The pack after 150 charge cycles altogether is yielding lowered range for the scooter. In another thread it has been proposed that individual battery leads can be attached while still connected in series. The purpose is to provide an equalizing charge to each battery at up to 16V at 1 amp or less.

Could someone with experience/education weigh in on whether this is a good idea? I am concerned about the result with the series wiring still in place.

colin9876
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Re: VRLA equalizing charge: series connected

If you get a single 12v car battery charger then you can top each battery up.
Doing one at a time, you can do this while they are series wired, and it will indeed help balance the pack.

randalson
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Re: VRLA equalizing charge: series connected

Great - thanks. I have a variable power supply on the way to do the job. I have to dig into the scooter to attach the leads and figure a good way to mount them for easy but safe access with the body work back on.

Anyone having any other tips for this process please feel free to weigh in.

e-doggies
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Re: VRLA equalizing charge: series connected

If they are non-flooded, and non-refillable, I don't think an "equalization" charge is recommended. 16V is way too much for AGM's or GEL's. Continuous charging and discharging in series is death on lead batteries in my experience. I've been parallel charging with one 12V charger for about 3 years. Many of the batteries in my scooters came from Craigslist scooters that had "dead" batteries (there's usually one really bad battery in a pack). Once the initial wiring is done, parallel charging is really quite simple and foolproof.

You can leave your batteries wired in series and safely attach a single 12V charger to ONE battery. If you parallel charge all the batteries together with one 12V charger, you MUST disconnect all series interconnects FIRST!

Individual or parallel charging will help to balance the pack, but there may also be other damage that has been done. Series charging can leave one or more batteries in the string undercharged which leads to more sulphation and loss of capacity. I've been having good luck with a BatteryMINDer #12248 charger/desulphator. On a 20Ah SLA, it increased the AH capacity more than 25% in about 3 weeks. They are pricey at over $100, but cheaper than 5 batteries. I put a Watt meter in series and I can monitor voltage, amps and accumulated Ah's.

randalson
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Re: VRLA equalizing charge: series connected

Thanks! So, e-doggies - are you always parallel charging now, no series charging? The idea from the other thread was to full charge in series first, then push each battery. (A different one each day, rotating through.) Where did you put your watt meter, and what make and nodel? My batts are BB brand EB-50-12 (50aH VRLA.)

colin9876
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Re: VRLA equalizing charge: series connected

I agree that a final voltage of 16v would be too high, But you can use a 16v source to push the current through to charge. I would have just used a single car battery charger because that will stop at the correct final voltage for you.

What your trying to do is get each battery at the same voltage (Balanced). So charge the pack and then put the charger on the low batteries till they are all about the same (you'll probably be aiming at about 14.2v each)

So to top up, use your power souce for say 15mins, then take it off and read the voltage, and carry on doing that until youve got the required voltage.

And that thing about 'doing one each day' is crazy Baloney! The whole point is to get the cells balanced so you want to do the whole thing in one go.

Parallel charging is in theory the best in an ideal world - but it requires rewiring.
An equalization topping up every couple of months or so is a pretty good second best.

JUST A THOUGHT, can you measure each battery voltage with a voltmeter and post the values here, then we can see how out of balance the pack is??

e-doggies
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Re: VRLA equalizing charge: series connected

Yes, I re-charge every time in parallel. Since I discovered this (here on V about 3 years ago), I have not used a series charger one time. My scooters are smaller (the largest pack I have is four 12V 20Ah), and I use 10AWG wire and 45A powerpoles to rewire the pack. That would not be nearly heavy enough for your use. 75A powerpoles may be heavy enough, but having 10 of them together in one plug will be bulky, hard to connect/disconnect, and possibly prone to getting very warm during high amp draw.

If you search on "parallel charging" I think you will find some good old threads that talk about this in more detail.

"Battery equalizers" are supposed to keep series-charged batteries in balance. You would need one less than the number of batteries you have. I haven't seen equalizers talked about much recently. Does anyone still market them? IIRC they were an expensive option.

The Watt Meter I use is a Turnigy 130A that I bought from HobbyKing. It's a nice little bench tool. I just connect it in series between the charger and the batteries. I also connect it between the batteries and an inverter when I want to do a controlled, measured discharge.

mf70
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Re: VRLA equalizing charge: series connected

As previous commenters have said, blindly dropping 16V across a battery is not a good idea.

I have come out a number of times for parallel charging, serial pack. Yes this requires rewiring, and a little literal hacking; however, in my case at least, it meant replacing the inadequate 14GA crimped wiring with 10GA soldered, which can only increase effective power output from the pack. (Admittedly, the hair-thin phase wires to the hub motor cannot be changed, but every bit helps.)

The trick is to have a common plug on the battery pack wired in parallel:

Battery box

This then connects to the controller through a series jumper plug:

series jumper

The charger is connected in through a similar plug wired to provide 12V to each battery in parallel:

Charge plug
(This was an older version, where I used four chargers in parallel - a single charger is much better!)

Access to the plug area is through a hole carved in the belly, visible in this pix:

side

colin9876
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Re: VRLA equalizing charge: series connected

@mf70, very impressive, thanks for posting those photos.
where did u get the connector blocks from that u wired the batts to in series and parallel for the different setups?
I made two messy harness things for the different configs but ur block looks better.
perhaps u could go into business making them lol!

randalson
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Re: VRLA equalizing charge: series connected

Wow - excellent stuff, all!

I was just thinking of running a pos and neg wire from each batt out to a convenient place, blocking them so they can't touch of course. Then I can both measure and boost as needed. Does that sound feasible to you?

The advice about equalizing all before running is good. That can easily be done over a weekend when I am not riding. I will watch the voltage boost - maybe 14.5 and see how that does.

I will dig into the bike in the next couple of weeks, so stay tuned for initial readings. Thanks again!

mf70
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Re: VRLA equalizing charge: series connected

Those are Anderson PowerPole 30A connectors. They are made to be "configurable" so that you can set up whatever arrangement you like. They are quite sophisticated. I used audio XLR connectors before, but they failed in a number of ways in little over a year of use. I have had almost two years with the Andersons now, and there is no sign of failure at all. They are available from "Powerwerx.com". They also have very high quality wire of all gages.


I was just thinking of running a pos and neg wire from each batt out to a convenient place, blocking them so they can't touch of course. Then I can both measure and boost as needed. Does that sound feasible to you?

You could do this with the Andersons, but you would have to charge each battery separately still. After that trouble, it would be a trivial amount extra effort to make up the series plug and the parallel charging plug to be confident in the balance of the charge. Switching plugs actually rewires the pack so there is no chance of shorts.

mark

colin9876
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Re: Andersons

@Mark, looks good that powerwerx site, what I cant tell is how you've managed to get 8 of these connectors in one block. You say they are 'configerable'? Does that mean they clip together, or did you glue them together into a block or something?
If you're able to post a another pic of those series / parallel blocks and how you wired them it would be really useful

@Randalson - what you say sounds fine, but if you can get to the batteries easily enough you dont need to solder on extra wires. Just hold the voltmeter on to the batts to get the readings, and then you'll probably find you only need to touch the charger on to any lower batteries for a few minutes to balance them up.

Oh and just a word of caution, make sure you put the neg charger lead to the -ve battery terminal, and poitive to +ve. Ive blown chargers INSTANTLTY by connecting them the wrong way! I always use a voltmeter to check the volt readings across the battery and the charger leads are the SAME SIGN (i.e. both +ve or both -ve depending on which way round Im holding the probes) before connecting!

randalson
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Re: Andersons

@colin: battery access is a multi hour bodywork wrestling event. Thus the desire to have leads run up through the tray and accessible under the seat like the existing charge port. Just to confirm, I plan to leave the series wiring and charging system in place, then measure and equalize each batt after standard series charging. thanks again.

colin9876
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Re: VRLA equalizing charge: series connected

@Randason, You really dont need to do an equalisation every charge (unless you want to of course). They wont slip out of sync that quickly unless one battery really is bad.

By the way, this may be stating the obvious, but some people find it easier to Run the higher batteriess down (with say a 12v bulb), rather than charge the lower ones up. Once youve drained a bit from the highest ones to get them balanced you can just give the pack a series top up.
I mention this because its cheaper to pick up a small bulb or resistor, rather than buy a single 12v charger if someone doesnt have one!

mf70
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Re: Andersons

@Mark, looks good that powerwerx site, what I cant tell is how you've managed to get 8 of these connectors in one block. You say they are 'configerable'? Does that mean they clip together, or did you glue them together into a block or something?

Yes. They are like Legos, with additional housings and clips to make each contact assembly a solid unit, and to provide a way to attach each contact assembly as needed. In my case, I "jiggered" the contact block a bit to make it stick in the battery case, but not interfere with removal of the case or removal of the contact block when needed.

Mark

fivari
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Re: VRLA equalizing charge: series connected

@mf70: you found a very conveniant and cheap solution for balancing your batteries. However, I have one question before I go for the same solution. Imagine your batteries to be quite out of balance after a ride. If you connect your parallel adaptor, I would expect some sparks and high current since there is no resistance between the unbalanced batteries. Did you ever noticed this?
Thanks
Fivari

Two e-scooters 1500W 48V 30 Ah LiFePO4

colin9876
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Re: VRLA equalizing charge: series connected

Parallel balancing doesnt mean 'sparks' flying because cell imbalances are proportionally small and V=IR means the current is proportional to the voltage differences.
The batts have a certain amount of internal resistance. and with a difference between say 12.1v and 12.4v is only .3v and so the current is single figures amps AT MOST.

Its worth checking if your batts are even out of balance. Lead Acids dont last that long, 400cycles if looked after, it may be they are just getting old

mf70
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Re: VRLA equalizing charge: series connected

No I have never seen this, probably, as mentioned, because they aren't allowed to get that far apart.

On the other hand, the situation you're describing is analogous to "dump" charging where a pack is bulk charged from a larger battery pack rather than transformed 110 volts. This CAN lead to amazing amp flows if the target pack is fully discharged. I've never done it, but the EV list had a correspondent that had an electrically powered lawn mowing service. He traveled by an electrically powered pickup. After about 40 minutes of mowing, the mower was recharged from the truck's pack. It didn't take long! It doesn't hurt the pack if the voltages and chemistries are compatible.

irab
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Re: VRLA equalizing charge: series connected

Here you will find a link to the Dutch Electric Scooter forum with details regarding a quadro charger. (In Dutch)
You have to register to see all the diagrams. However, some of the diagrams are visible because they are linked to an external server.

http://www.elektrischvervoernederland.nl/forum/viewtopic.php?f=193&t=848&sid=f62f9aacc1e992218aad86fcadbd2531&start=40

Regards,

irab

mf70
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Re: VRLA equalizing charge: series connected

I tried this and was disappointed. The failure mode if one of the four chargers isn't optimum is blowing the entire pack.

Rewiring for series/parallel is a pain, but the result is smooth and reliable with Anderson PowerPole connectors.

Mark

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