Hi Steve,
It is a better option to feed the traction bank. Charging for your house off the traction bank is the best way to keep your navigation equipment working while under way so putting the energy into the traction bank kills two birds with one stone.
If you are just learning might I suggest panels designed for grid tie. Not that lower voltage panels can't grid tie making my statement a little off but... High voltage panels that will charge your bank without a conversion will reduce losses. 95% efficiency from voltage converters can be avoided by choosing a panel that produces the voltage you are needing. Might I also suggest looking at the selection of products Sun electric has to offer(no affiliation). MPPT controllers(Maximum Power Point Tracking) controllers are the best choice for any solar set-up.
A controller for each panel will keep one panel that is partially shaded (one cell is all that is required) from bringing down the complete system. Not unlike one bad cell in our storage bank killing the complete bank.
It is true that MPPT controllers will modify the output voltage, but there are limits, so don't buy without personally investigating each controller you think will work. It is easy to get boondoggled into equipment that has features you don't need, or equipment the seller himself does not understand. Most controllers claim the ability to control more than one panel systems. This is a claim for uninformed buyers, don't be one of those, understand what they mean before you design your system. I can not fill in this blank because each controller is a different breed, with only the concept linking them together.
Remember the higher the voltage of any part of your system the smaller loads every part like controllers will have to sustain. i.e. control FETs and electrical components are rated for Amps at a rated voltage. So are wire and fuses.
Best of luck with your system
Kevin Pemberton
On 06/27/2012 06:53 AM, Steve Dolan wrote:
I've just started to learn and consider solar panels for Electra Glide and could use some input from you guys. I would like to go with 2 panels, probably the Sun 210's giving me 420W total off my dingy davits.
The current system:
I have 144V pack of 12 AGM's but plan on a LiPo4 pack in the future as my propulsion bank. I also have 3 AGM's for my house bank at 12V. The Propulsion bank charges the House bank through a charger/converter (144V to 12V). The shore, regeneration, and genset charge the propulsion bank.
Ideally I would love to charge the Propulsion Bank but if my math is correct I'll only get about 3A at 144V to the bank from solar. The same 2 panels will give me about 35A at 12V if I connect to the House Bank.
Most of the loads during sailing come from the house bank but I don't think I'm using 35A worth of electricity at any time so a lot would be wasted.
Questions:
Does it even make sense to consider going to the Propulsion Bank?
Most solar panels I've seen in the higher Wattage are 24V or higher, does the MPPT convert this to 12V output?
If the MPPT does load diversion (diverting power to a device such as a water heater or frig (Load Dumping?)) is this normally a connection at the MPPT of the device or does the device know not to get power from the house bank at the same time? This part is really confusing to me, I guess with a HWH you can control the device power input with a thermal switch but if I wanted to run a frig it has no such shut-off switch. For that matter what happens when you don't have sun for a few days and the wife just used up the 11gal tank?
Like I said I'm just know getting into this and think that the solar panels are the way to go it's just confusing on some issues.
Thanks in advance,
Steve in Solomons MD
Lagoon 410 SE
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