Trying to get the most out of the TV alternator

[charliem]

[quote source="/post/1570/thread" timestamp="1403107169" author="@tinkeringtechie"]There are plenty of adjustable boost circuits available on Amazon, but I'd be worried that I might overcharge the TT battery unless it was multi-stage. Which made me realize that my solar charger is multi-stage and I believe has a boost circuit built-in. I wonder what would happen if I hooked up the aux battery as the "solar panel"... would it boost and charge the TT battery using the aux battery as the source? I guess it's worth a try.[/quote][font face="arial" size="3"]Can you point to a real boost converter available on Amazon? Power in > Power out; Voltage out > Voltage in, Current in > Current out.. [/font][font face="arial" size="3"]Everything I find searching for "battery booster" looks like just a battery in a case that you connect to the vehicle battery in normal jumper mode. Most have a built in battery charger for the included battery. A device capable of supplying significant charging current at 14V or greater from an input less than 13V would be great for overcoming cable drop. The TV alternator usually has plenty of power available, but the system voltage is too low for quick charging of the TT. Maybe the MPPT solar controllers could be adapted.
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[tinkeringtechie]

Here are a few that I was looking at:

http://www.amazon.com/LM2577-Adjustable-Step-up-Converter-Module/dp/B008HMETBE/ref=sr_1_8?ie=UTF8&qid=1403137786&sr=8-8&keywords=dc+boost
http://www.amazon.com/Automatic-Converter-1-25-20V-Adjustable-Regulated/dp/B00K6ARMX2/ref=sr_1_11?ie=UTF8&qid=1403137786&sr=8-11&keywords=dc+boost
http://www.amazon.com/10-32V-12-35V-Adjustable-supply-Mudule/dp/B008BFNP62/ref=sr_1_7?ie=UTF8&qid=1403137786&sr=8-7&keywords=dc+boost

I already have this MPPT solar charger that I'll try:

http://www.amazon.com/Tracer1210RN-Solar-Charge-Controller-Regulator/dp/B008KWPGS6/ref=sr_1_1?ie=UTF8&qid=1403137925&sr=8-1&keywords=mppt

[admin]

Even if there is an option to boost the charge of the TT while draining the mobile battery it still seems like the idea is over complicating things.

In my mind I keep running two situations, in one you could rig up the system so the batteries are both mobile and thus you switch them out as they get low. Similar to a propane tank in concept. The down side to this is that it requires a fair amount of effort to move heavy batteries, as well as some pre-planning to have quick connection/disconnection to the electrical system. If its done right you could use them in parallel as well.

In the second situation I picture a single mobile battery that is used to increase the capacity of the overall system. The down side here is that you never get the TT battery fully charged.

I'd personally rather deal with switching the batteries out like propane tanks vs. adding more complexity with a booster. Now if the solar charge controller idea works, that seems like a slick way to solve all the problems. Providing that boost charge from a variety of power inputs seems to good to be true though.

I'm interested to see how that turns out.

[pinstriper]

Two propane tanks with a selector valve, you run one until its empty, then switch to the other.

Two batteries with a switch, start out fully charged on both. Drain one, flip the switch to bring the other fully charged battery online. Hook your solar charger up to the empty battery, let it recharge all day while you draw down the other. Lather rinse repeat.

Of course, you have to be able to monitor their charge when you get back on power (from TV or shore power) and switch to the empty battery to recharge it when the first is full.

For propane tanks I sometimes take them to a refiller, but I also just swap them via Blue Rhino or similar either out of necessity or convenience. The self-serve they have at many Home Depots are open 24 hours a day. It also means you never have a tank long enough to worry about rust or recertification. It is not the most economical way to go, but I don't go through propane that often for the difference to really add up.

[tinkeringtechie]

[quote source="/post/1590/thread" timestamp="1403184007" author="@admin"]Even if there is an option to boost the charge of the TT while draining the mobile battery it still seems like the idea is over complicating things.

In my mind I keep running two situations, in one you could rig up the system so the batteries are both mobile and thus you switch them out as they get low. Similar to a propane tank in concept. The down side to this is that it requires a fair amount of effort to move heavy batteries, as well as some pre-planning to have quick connection/disconnection to the electrical system. If its done right you could use them in parallel as well.

In the second situation I picture a single mobile battery that is used to increase the capacity of the overall system. The down side here is that you never get the TT battery fully charged.

I'd personally rather deal with switching the batteries out like propane tanks vs. adding more complexity with a booster. Now if the solar charge controller idea works, that seems like a slick way to solve all the problems. Providing that boost charge from a variety of power inputs seems to good to be true though.

I'm interested to see how that turns out.
[/quote]My electricity demands are pretty minimal, so having two full-size batteries would be overkill and too expensive. I might use 10AH a day maximum (I disconnected my fridge frame heater if you're wondering how I could get that low). If it's sunny I can replace that with my 30W solar panel pretty easily. But if it's cloudy or rainy it would be nice to have a backup charging method. I would pair the boost circuit with a cheapy SLA (maybe 20AH). That way I could add back my 10AH without draining the mobile battery below 50%. Total cost would be around $50 and could be easily moved back and forth. I already have a SAE connector on my battery for the solar charger, so it would be plug and play.

[admin]

I am all for multiple ways for recharging the system, which made me start thinking. I have a small inverter style generator that I believe was put out by Chicago Electric (Harbor Freight). Its basically a Honda knock off clone. It has a small outlet that is labeled as 12v but I've never seen this type of plug before; The two prongs are in a V shape. Have any of you seen this kind of plug and know where I could get a cable for it, and do you think it would require a charge controller for realistic use? I like this idea of being able to charge the batter from another battery, but if the generator is capable of doing it directly I'm thinking that might also be a good option since it sucks so little gas. Having the small generator could be useful if you aren't doing enough driving to fully recharge the mobile battery.

FYI I cant seem to find the same model I have when searching online. I'll try to pull a part number.

[tinkeringtechie]

[quote source="/post/1593/thread" timestamp="1403200358" author="@admin"]I am all for multiple ways for recharging the system, which made me start thinking. I have a small inverter style generator that I believe was put out by Chicago Electric (Harbor Freight). Its basically a Honda knock off clone. It has a small outlet that is labeled as 12v but I've never seen this type of plug before; The two prongs are in a V shape. Have any of you seen this kind of plug and know where I could get a cable for it, and do you think it would require a charge controller for realistic use? I like this idea of being able to charge the batter from another battery, but if the generator is capable of doing it directly I'm thinking that might also be a good option since it sucks so little gas. Having the small generator could be useful if you aren't doing enough driving to fully recharge the mobile battery.

FYI I cant seem to find the same model I have when searching online. I'll try to pull a part number.
[/quote]I think this is what you're looking for:

http://www.amazon.com/Honda-Generator-D-C-Charging-Cables/dp/B0044U4D2I

But if you've got a generator, why not just plug the trailer into it and let the converter do the charging?

[charliem]

[font size="3"][font face="arial"]My 2013 Tacoma with off road package came with a built in 400W inverter. With a 50% SOC dual GC2 golfer battery the TT converter delivered approx 20A charging. Switching to 16 foot #6 jumper cables to the TV battery gave approx 30A charging at idle. I just bought a 20 foot #4 jumper cable. Haven't tried it yet, but I've got lots of options. The #4 jumpers should charge the best; the on-board inverter is the easiest. The truck burns about 0.5 GPH idling. It's a lot easier to fill up the truck than to haul a genny and its gas can. Not as efficient or cheap, but no generator or solar expense either. Options!
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[tinkeringtechie]

Options are good and bad at the same time. Good that you have choices, but bad that you have to make decisions. This year our off-grid camping is pretty minimal, so I probably won't change anything yet. I might turn this into one of my winter projects and have it ready for next season. I'm picturing a little black box with a cigarette lighter plug and an SAE connector. Plugging the cigarette plug into the TV will charge the battery in the box, and plugging the SAE plug into the trailer will charge the trailer using the battery in the box. I'd also like to upgrade my solar panel from 30W to 100W.

[admin]

If you charge the battery with a cigarette lighter won't you have to drive a significant amount of time to put any real charge back into it? Assuming you've used it to top off the TT battery which would leave the mobile battery at a significant discharge.

[tinkeringtechie]

[quote source="/post/1597/thread" timestamp="1403204899" author="@admin"]If you charge the battery with a cigarette lighter won't you have to drive a significant amount of time to put any real charge back into it? Assuming you've used it to top off the TT battery which would leave the mobile battery at a significant discharge.[/quote]That's a good point, I'd be limited to 8 amps or so continuous from the lighter. Hmm... I don't think I have any room in the engine compartment and I don't really want to make any modifications to the vehicle. Maybe the battery plugs into the 7-way? More planning required...

[admin]

I think the 7 way circuits are limited to 10 (maybe 15) amps if given the right control unit. When I was getting a wiring harness for my Pilot I remember reading a couple warnings about the limits of the power output from a 7 way connector.

The output from the lighter is better than nothing, and its the easiest way to get started.

[david]

Where do you guys use all of the power so that the standard 70 amphour battery mounted on the a-frame isn't enough. We haven't camped long enough in one spot for it to matter. But with LED light, a fraction of an amp for refrigerator control, a few amps every time the hot water heater or the water pump goes on, we probably use only 10 amp hours a day. That will easily be replaced via the TV connector with a few hours of driving.

I agree wit another poster's comment about adding another 6 gauge circuit directly from the TVs battery to the trailer's battery (fused at both ends of course). Pin 7 (methinks) will provide 30 amps, but that only lasts for a short while due to voltage drop in the 10 gauge wire. #6 with a 100 amp fuse on both ends should halve the TV's running time to recharge. But it won't be easy to run those wires. And I say wires because you have to have a #6 ground wire as well as the pos wire.

David

[mitch]

Hi David,

The fridge will use about 12 amp hrs per day by my figuring.  There's a thread somewhere where I posted what uses how much and some assumptions I made and I came up with using about 20 amp hours a day being relatively conservative.  On a 70 Ahr battery you technically should only use 35 Ahrs before charging to avoid battery damage so that only gives you 1.75 days (the battery that come on my 13qbb was 85 Ahrs).  If you can't find the previous thread and want the info let me know and I'll dig it up.

Mitch  

[tinkeringtechie]

[quote source="/post/1787/thread" timestamp="1404251915" author="@david"]Where do you guys use all of the power so that the standard 70 amphour battery mounted on the a-frame isn't enough. We haven't camped long enough in one spot for it to matter. But with LED light, a fraction of an amp for refrigerator control, a few amps every time the hot water heater or the water pump goes on, we probably use only 10 amp hours a day. That will easily be replaced via the TV connector with a few hours of driving.

I agree wit another poster's comment about adding another 6 gauge circuit directly from the TVs battery to the trailer's battery (fused at both ends of course). Pin 7 (methinks) will provide 30 amps, but that only lasts for a short while due to voltage drop in the 10 gauge wire. #6 with a 100 amp fuse on both ends should halve the TV's running time to recharge. But it won't be easy to run those wires. And I say wires because you have to have a #6 ground wire as well as the pos wire.

David[/quote]I don't think we're using much power, we just stay longer in one spot. Even with your 10Ah/day figure that's about 3 days before you'd need to recharge. If you're moving more often than that, then you need to find more interesting places to stay 

Also, you don't need to run the ground wire far; the frame is nearly zero resistance. Running all the way to the battery would actually cause more voltage drop than grounding to the frame close to the connector.