charging 48v SLAs

[Jay64]

This might be a dumb question, but I gotta check. If I have 4 12v SLA batts in series to make 48v, does it matter on which terminals I connect a 48v battery charger to? Right now I only have a 12v battery charger, so I was thinking I would just disconnect all the batteries and charge them each seperately. But the more I thought about that, the more I realized what a pain that would be, so I started thinking about getting a 48v battery charger. When I started picturing in my head how I would connect it to the 4 batteries I started to wonder if it had to be connected at the + and - end of the series string. Meaning, do I have to connect the charger to the same termials that the controller connects to, or could I just connect it to any + and - terminal in the pack? The way the bike is currently set up, it would be a LOT easier if I could just connect it up to any + and - terminal in the pack.

 

[Jay64]

Actually, now that I think about it, I do have a 48v battery charger. It is a 48v Soneil SLA battery charger that supposedly was modified to charge LifeBatts. Would it still be able to be used to charge SLAs, or did the modification make it unuseable for SLAs now?

 

[nomad85]

You would probably need to open it up and change the voltage output, someone more experienced might be able to tell you what voltage it needs to be at. I would guess around 54-55v its probably at 58-60v now.

 

[frodus]

I think lithium chargers have a different charge profile... not sure.

For the 48V charger though, you would have your series pack with B+ being the top of the pack (bat 4 positive) and B- being the bottom of the pack (bat 1 negative). Connect charger to B+ and B-. Controller connects after the contactor. Don't connect the charger on the wrong side of the contactor or it won't charge.

 

[Jay64]

So I do have to connect the charger at the end of the string then? I thought that might be the case. I guess I will redo the wiring more like the connections of the electric order picker at work. Unplug the batts from the bike cirucuit and plug that into the charger plug. Yeah, I meant the leads that went to the rest of the bike circuit. The B+ at the top of the pack goes to the contactor and the B- at the bottom of the pack goes to the B- on the controller. I guess that's why I just said going to the controller.
I found a few 48v SLAs chargers for scooters. But they all seem to come with the 3 prong plug. Would I be able to just cut this off and connect it directly to the B+ and B- terminals, and if so, what is the 3rd wire for?

 

[frodus]

The one on my 24V charger is not attached, just + and -. Its just a cheap connector, thats why its used. Some might use it for remote temp sensing.

Remember to fuse the charger from the battery pack.

 

[vanilla ice]

You dont got to disconnect any wiring to charge individual 12v sla's when they are hooked up in series. Just put those alligator clips right on the terminals. Or if its a physical access problem you can have leads coming out like the balance leads on a lithium pack. For the 48v charger you deffo gotta connect it to the extreme end terminals of the pack.

 

[Lessss]

If you run a second set of cables to each battery then you could use the 12 V charger to charge each one indivually. This would also keep your battery pack in better balance. I recommend you do this once every 3 to 6 months anyway.

 

[Jay64]

Frodus, what do you mean fuse the charger from the battery pack? Put a fuse inline between the charger and the battery pack?

VI, it was more a matter of an access problem. But I could just have some charge leads coming off the B+ and B- like you mentioned. I will probably end up doing that.

If you run a second set of cables to each battery then you could use the 12 V charger to charge each one indivually. This would also keep your battery pack in better balance. I recommend you do this once every 3 to 6 months anyway.

So I can have all the batteries hooked up in Series but also have a second set of cables to each battery then I can use a 12v battery? I don't understand how that would work if the batteries are still hooked up in series. Even if I have seperate cables going to each battery, wouldn't they still be tied together by the main cables connecting them in series?

 

[vanilla ice]

Yup, thats how I charged this 54v SLA mongrel:

http://home.mindspring.com/~vanillaice/crap/steed.jpg

With nothing but 12v chargers and a 6v charger too. Balanced every charge sort of like xy's individual chargers. Well not down to cell level cause they're SLA, but still. Can't say I ever tried running it while charging but I don't see why doing even that would cause any problems. No worries, you can even use two chargers on the same battery to double up the charge rate.

 

[Jay64]

I can use one charger and charge each battery one at a time while they are wired together, or I need one charger per battery and charge them all at the same time? Sorry bout all the questions, just trying to make sure I understand it right.

 

[Ypedal]

Yes.

You have 4 x 12v SLA's in seried

Negative--- [- +]-[- +]-[- +]-[- +] +++Positive


Just like my PSI cells.. just run a + and a - wire from each post of each battery and plug a 12v charger to each one.. or one at a time if you only have one charger. ( This may suck as you would be leaving some cells in a discharged state while they wait for their turn )

The modified Soneil charger would charge your 48v, actually would slitly overcharge them a bit but this is not a huge deal to sla's.

 

[vanilla ice]

Yeah Jay you don't have to disconnect any bike wiring to charge. And you can charge one battery at a time or all together. It will work fine either way. Only thing is, like Y says one at a time means your other SLAs will be waiting there discharged and they don't like that. But I did that and it worked out fine.

When I top off my in-storage motorcycle's starter battery with my little low current chargers I connect two or three simultaneous like so it will go faster.

 

[Jay64]

Ok, cool. I will probably just use my Soneil, I was just trying to understand everything a little bit better to give me more options.

 

[Jay64]

That brought up another thing that I have been pondering. I wanted to get a solar panel charger to be able to plug in to the bike when I park it in the parking lot for the day at work. I figure I live in the sunshine state, I might as well take advantage of it. I found a bunch of small panels for sale at places like Autozone and Harbor Freight. But I could only find 12v or 24v. So I was thinking that I wouldn't be able to do it for the 48v pack. So does this mean that if I get 4 12v solar panels I can have them plug into each battery while all the batteries are all connected together? I know it wouldn't be the same as plugging in chargers to 110v, but I just really like the idea of charging my bike while it sits in the sun while I'm working. And SLAs aren't supposed to sit not fully charged, so it would give me a chance to at least put some charge back in while at work. And, at the moment, I only live about 4 miles away from work, so I guess I wouldn't use up too much of the charge and the solar chargers might be able to recoup that while I am at work.
So...short story long, will that work?

 

[frodus]

Frodus, what do you mean fuse the charger from the battery pack? Put a fuse inline between the charger and the battery pack?

Yup

You should always fuse to protect the bats, if something shorts, your bike goes up in flames.

Fuse protect as close to the pack as possible for the charger AND for the controller (on the bat side of the contactor). Basically protect for charge/discharge.

 

[frodus]

also, those solar cells are likely below 20W, even if you did hook em up, thats only 1-1.5A of charging... it'd take days to recharge.

They're meant to keep batteries topped off in cars when they sit for long periods of time. They're just not small and efficient enough YET for EV use.