The only fear I have is that over charging it might cause permanent damage to the very expensive battery. Most lap top computers and cell phones have smart chargers that sense when the battery is at capacity and it is a known fact that over charging those batteries can cause permanent damage. I might chance it. But I think I will give my Honda dealer a chance to rectify the problem first.

 

As long as you keep the current at 350mA or lower, there will be no damage what-so-ever.

what happens is, the fully charged cells are designed to dissipate any extra current into heat, while the weaker cells catch up.

In both the Robert Smalls posting, and many NiMH articles, they state that you can do this 'top off' charge for up to 20 hours as long as the current is small.

 

Hi Jeep Daddy,

I've been away for a while... sorry about that. So many projects... so little time.

I agree with you that I may have gotten a good "junk" battery and put it in my car. I have very few recals even today. I haven't done anything but drive it... no trickle charging.

The old battery sits mostly dismantled in my basement crying to me to put it back together.

I have the new battery tester and haven't even played with it yet. Spent some bucks on that thang! What's wrong with me! :-)

Currently I'm building a RepRap 3d printer. Don't get me started!

So my two cents... I suspect Jeep Daddy that one or more sets of cells (double-sticks) are discharging faster than the rest, causing an out-of-balance battery pack in short order. Once the battery is out of balance, the recals begin and don't go away.

It's possible that wacking away at it with bigger charges could break up the crystals in the battery chemistry and maybe bring some useful life back into the cells, but maybe not. I understand that the crystals can grow and start to break through the insulating barrier shorting out the cell (causing the cell to discharge faster?).

What I planned to do (and haven't done yet... :-P) is charge the sticks and discharge them through the battery tester graphing their outputs. I would do this several times varying the conditions of each test... such as allow them to sit for several days after a full charge and then discharge them through the battery tester. That should tell us something interesting.

Right now folks I'm spending every waking moment on other projects and work. I'm gonna seriously crash soon!

I'm still keeping up with the forum... just haven't been posting in a while.

Good luck in your efforts!

Ross

 

Here's a couple of pictures of my trickle charger. There's really nothing to it. The reason there's nothing to it is because we're filling a 20 gallon tank with a teacup. Trickle charging is just that... putting a small amount of charge into the pack. It's such a small charge that we don't have to worry about overcharging or overheating the pack.

If we were trickle charging a single cell... well now... that's a different story. Store bought chargers for charging those flashlight and music player batteries have to have thermal sensors and carefully watch the charge curves to prevent overdoing it. Not the case with a battery pack from a civic hybrid.

I say all of this stuff because I too was nervous about how to treat batteries when this adventure started. I'm trying to share what I have learned.

So, here's my trickle charger... pics below:

 

Explanation of the circuit above...

The first picture is of the trickle charger. It's components are a power cord, three 48vdc power supplies, one constant current supply and some wire to wire it all together.

The power cord is connected to all of the supplies in parallel. Essentially every supply gets power.

The supplies are then connected in series together such as the positive output of one is fed into the negative input of the next... this repeated for each of the supplies until you have only the original negative terminal of the first supply and the ending positive terminal of the last supply that is not connected.

Those connections are wired to the pack, positive to positive, negative to negative.

The power supplies connected in series add their voltages together. So 48 plus 48 equals 96 volts... plus another 48 equals 144 volts. Then there's that last supply... the constant current supply. It's also wired in series but there's a hitch... it puts out a variable voltage to maintain a constant current output of 310 miliamps. It's voltage can vary from 3 to 36 volts. So our total voltage supply is 147 volts to 180 volts.

The trickle charger will adjust it's voltage to be slightly higher than the pack voltage so that it can push 310 miliamps of current through the pack. It's a bit like two aquariums connected with an underwater pipe. Left alone, the water level of each aquarium would equalize and there would be no flow through the pipe. But if you raised the water level in one tank above the level in the other, water would start to flow into the other tank.

That's what this charger does. It raises it's voltage above that of the pack so that it can feed the pack with a small charge current.

I hope that helps explain this stuff. I'll get a simple diagram up in the next day or so to help with wiring your own charger.

Regards all!

Ross

 

Ross

Outstanding!!

Great info. Much thanks.

To confirm I understand your set-up, I used Microsoft "Paint" (please excuse the crudity of my wire diagram) to draw out your explanation onto your photo "P1180021".



Do I understand your wire set-up correctly?

Early mention has been made regarding "diodes". Where do they belong in this set-up?

Could you also snap a photo (for wire diagram purposes) of your controlled but fast discharge technique utilizing the two incandescent light bulbs.

Thanks!!!!

Mike

 

Mike I believe the diodes go between the charger and what-ever you are charging. Diodes allow electric to flow one way only. H

 

Harold has it right.

I put two diodes in series between the two wires used to charge the battery. I connected the diodes near the battery terminals and ran the wires long enough to run them behind the seat and extend just a few inches out near the door so that I could connect it when charging and tuck it when not in use.

The diodes have to be reverse biased to the battery to perform properly. The reverse breakdown voltage of a 1N4007 diode is 1000 volts. So it prevents the much lower pack voltage from pushing current through the wires. It's just a precaution.

I also used heavy wires with thick insulation. Not because the charger uses a lot of current... but because if the car was in an accident, I don't want these wires to get cut too easily. Again... the reason for putting the diodes at the battery terminals.

Navguy, the diagram is spot on. Thanks for putting that together!

Cheers all!

Ross

 

Ross/Harold

OK, thanks ref clarification on the diodes.

I check they are 'one way valves' so to speak, like a check valve.

I have added same to my diagram.

Ross, please confirm direction of the diodes in my drawing is correct.

Also, when I try and find the RECOM RACD12-350 350mA 3-36VDC unit in your set-up, for the life of me I cannot find that item at the digikey site. Could you provide a link to the unit please? Thanks Mike

 

Hi Nav,

The diodes are backwards in your diagram. You want the diodes to allow current from the charger but not allow current to return from the battery. Fix that and it's perfect! Thank you for doing this!

The Digikey part no. of the constant current supply is Digikey part no. 945-1374-ND.

http://Digikey.com



So here's a list of the parts from Digikey:

Digikey part no. 285-1823-ND LS50-48 $24.87 (3 required)
Digikey part no. 945-1374-ND RACD12-350 18.82 (1 required)
Digikey part no. 641-1312-1-ND 1N4007 .25 (2 required)

Let me know if anyone has any questions of if I left something out.

Regards all!

Ross