Battery chargers

[Drunkskunk]

I posted in another thread about looking for cheap batteries, and was given a great solution! it worked out to 36 cents a watt-hour. at the current price of SLA, that was even cheaper if you factor in the actual, usable wattage. I was ready to place my order, but hit a snag. Charging.

I want a charging system that involves no more work than plugging in one chord and leaving it untill its done, in less than 6 hours, and is portable. Easy and cheap for SLA, but darn near impossable for anything else.

the best I could find for Nicad was to have 5 chargers going through one 6 pin plug(common earth), but that wouldn't be cheap or portable, and the cost of setting it up began to aproach the cheap end of Lipo cells. with the plugs and accessories needed to get the chargers and batteries going, the whole setup was at the $500 mark. not so cheap anymore.

So I start searching around this forum and the net for charging information. I found plenty on the diffrent batteries, but almost nothing on chargers. Wityh all the info out there, and all the comparisons on cost per watt hour and so forth on the batteries, I'm supprised fewer people haven't taken in to account the cost of the charging system.

So is there something I'm missing on chargers? What are people using to charge there Nicads, there SLAs, there Lipos?

 

[jdh2550]

Good question:

As far as I know the important aspects of the charging cycle are:

1) Voltage profile required by the chemistry (x amount of time at y voltage for chemistry z)
2) Internal resistance of battery pack - which determines the maximum safe charging current for a given chemistry (heat kills batteries, current flow through resistance causes heat)

Also, good chargers have some "battery management" smarts built in to avoid overcharging. Some sense heat as well as voltage.

I guess my ideal situation would be to have the BMS as part of the battery pack (because a BMS has uses on both charge and discharge) and have a a power supply that one could program a flexible voltage profile and vary the amount of amps delivered as well. Does such a charger/power supply exist?

 

[vanilla ice]

Now I leave my non-matching SLA's wired up in parallel/series and charge with a single 36v charger as is.

 

[Drunkskunk]

yesterday I emailed the guys at TrueRc about their Lipos. they have a 55v, 5 amp 15s1p battery that would be perfect, if I could run 2 in parallel. only about $1.15 per watt hour, too. Not too bad for a battery, considering its from a company I've delt with before and trust.

Today I got an email back. While they sell the 55v battery, they don't have a way to charge it. He did have some sugestions on third party chargers that could be ganged together, or to take the battery appart and retap it to charge 5 cells at a time, but essentualy, I'm SOL on charging.

All this great battery technology out there, and still charging seems to be a hit and miss process. is there something I'm missung here?

 

[fechter]

No, I think you have an accurate idea of the picture.

The method of using multiple chargers for sections of a larger pack is fairly common. You can make all the connections on a single multi-pin connector.

I use a pair of chargers for my 48v SLA pack.

A single 48v charger would be more expensive than two 24v chargers, and wouldn't balance the pack at all.

Since the charger(s) will last much longer than the batteries under most conditons, I'm willing to spend a bit more to get a nice one.

 

[monster]

i use three of these chargers for my 24v nihm bats, and they break more often than the batteries. i dont know of any other alternative. 1 has broken and 1 is on its way out.

 

[mvadventure]

At the heart of my continuing saga with Zane of Aten Energy and the potential eventual delivery of the LiPO4's ordered a couple of months ago is the charging system.

According to Zane my delays and delays of the past are because of the complexity of designing and developing not just the charging but the BMS (battery management system).

From reading a lot of the posts it seems to me that the BMS portion of the charging system is much more complicated and is a stability requirement for any type of lithium battery and some of the nickel formulas.

SLA however has been around a long time and was preceded by flooded cells so charging systems there, if not perfected, are more than adequate at reasonable prices. The Soneil 48 volt charger that came with my Phoenix Cruiser (Crystalyte 5304) charges four SLA bricks fairly quickly, guards against and corrects some sulfation and is pretty much bullet proof if I don't tear the connections out.

So, no, there is nothing YOU are missing here, it's the coordination within the industry as it relates to the ebike world which is still a very small part of any battery business. Chargers are not interchangeable within the various species of batteries and require their own development angst. With such a small market developers aren't rushing in to make it easier. Maybe someday. Maybe not.

However this is simply an opinion and like old Mustangs and washing machines, you either have one, had one or will get one.

Mike

 

[BiGH]

I second the annoyance of battery chargers - i've now had TWO of the chargers die on me - for the 4x 12v setup i have. Its making it increaseingly difficiult to charge them up properly.

I killed the most recent charger becuase i forgot to plug the 2nd pack in! and that was enough to nuke it.

I've got lithiums (2 lots now) on order so Im not really worried about this pack anymore (4x17ah 12v slas) as they will get used in the solar /wind array i'm planning, and the first pack of lithium will arive on wed-fri

I would personally spend big money on a good quality battery charger that was able to charge batts of varying chemistries (SLA, NIMH, and the lithiums) of pack sizes up to 48v as long as it supported:

1) the ability have one chemistry selected from a menu (firmware upgradeable for future chemistries),

2) plug in and automatically charge the battery (and potentially ballance it too)

3) work like a float charger if it is apropriate for the batteries

4) not blow up if you mess up something obvious - like forgetting to plug the battery in before turning the unit on - it should sense this. (clearly there isn't anything that could be done about selecting the wrong battery type).



I'm really piissed off about the chargers dying like that. From what i hear its hard to get good chargers that won't die easily - they're all sensitive.

 

[Eric G]

I've had 2 sla chargers go belly up within 3 months of buying them.They weren't cheap ones either ~$50. each. Returned both and the replacements have been fine since.

The one would only bring up the voltage to about 13.6 volts then go to green light (charged)when in fact it was under charged.With the other one the voltage just kept going up and up caught it at 16 volts Phew.... seems no harm was done to the batts.That charger was an automatic one that was supposed to go to a float after reaching 14.4 volts.

I've never truly trusted a charger since and check them with a DMM or hook up the Watts Up to monitor the charge.

Eric

 

[recumbent]

I second the annoyance of battery chargers - i've now had TWO of the chargers die on me - From what i hear its hard to get good chargers that won't die easily - they're all sensitive.

I third the annoyance of battery chargers, but only had one die on me.

I'm also going to (possibly) purchase a multiple chemistry or at least have variable voltage charger, hopefully are built better with proper protection.

What kind of lithiums did you buy? I'm getting some in a few months but not positive which chemistry.

 

[BiGH]

Both are lifepo4s... one from yesa, one from solarbbq.

i'll report more when i get them

 

[monster]

i'm looking at building my own chargers because the stock NiHM chargers are so unreliable. i will convert SLA or drill chargers to temperature cut out and then use these http://cgi.ebay.co.uk/UNIVERSAL-MAI...ryZ96942QQssPageNameZWDVWQQrdZ1QQcmdZViewItem universal mains adapters to trickle charge at 0.3A

 

[monster]

or may be this http://cgi.ebay.co.uk/SKYNET-ADAPTO...ryZ96942QQrdZ1QQssPageNameZWD1VQQcmdZViewItem
which is 30v -for balancing the cells.

 

[Desertprep]

You read my mind! Now you have me thinking...I have seen some simple plants for diy battery packs but it seems to me that in their design they did not include any thinking for recharging the cells. Is there any way to modify the design of a battery pack - including the case - so that I include technology to easily charge the battery? For example if each cell is 1.5 volts and there are 20 cells is it possible to design the battery pack to use a charger that puts out 1.5 volts at lots of amps so that each cell is charged individually, with some kind of cut off for each cell to protect from overcharging?