Bump! (what is that?? lol) I tried this with the old charger but was unsuccessful, then pretty much forgot about it....I've seen this done by tapping into the charger on the DC side just after the transformer. Basically eliminating AC. If you search long enough on Youtube I'm sure you will find it.
He used 3 solar cells from memory charging a 36v battery. I think it was even on a bicycle trailer
If you are game, open your charger and see if you can obtain an unregulated DC voltage from the transformer, if this is the case you are cooking with gas.
If it's regulated, then you will need to match this value which is also not so difficult.
Cannot say for sure, but I assume the GM panels have either a suitable in-line charger or each cell group is regulated to output the correct voltage depending on the battery type.
Also you can safely charge Li-ion/po with a
small current providing there is no serious (more than 5%) over voltage, because its solar; there is no real chance of 'leaving it on too long' as night will come before any damage will occur anyway. You would never really want to use this to fully charge a battery from dead to full, more so to keep it topped up.
Saying this, why don't you try
one of these I tried finding the one I have (unused) that handles 10A (also around $10), but this one looks good too. Anyways have a looksy around the e of bay.
Using this you would put your panel in full sunlight, then adjust the output to 54.6V before connecting to your battery to charge. I don't know what kind of current you will get (or expect) but I assume it will be around 1A maybe less.
Ideally you want to tap into the charger, then you have the convenience of plugging AC - or your custom lead to goto your panel. Nice and neat
Cheers
