What size converter/charger do I need?

[Daebado]

The DW and I are wanting to get more into boondocking and eventually want to add about 200W of solar to our hybrid Shamrock 23WS and replace my current flooded lead acid battery with 100Ah LiFePO4. Combined with charge controller, invertor, etc. along with a generator for cloudy days, this will be a significant expense and I want to do it one step at a time.

As a preface, most of our trips are small, 2 to 4 day trips within a 6 hour drive from home with an occasional 7 to 9 day big trip somewhere (this year, it's Colorado).

To get started, I think I want to replace my battery, first. I'm assuming my present converter/charger isn't made for Lithium batteries (I haven't looked yet but will once the weather warms up a little) so I'm looking at something like a PD9160ALV. The main question I have currently is, how do I know if this is the right size for my needs? They make a number of different models. This one is 60 amps but they make them bigger and smaller.

Also, is there anything else I should be considering at this time besides the converter?


Thanks

[ependydad]

You can upsize the converter because lithium batteries can take faster charges. Check the specs on whatever one you're looking at to see the maximum amount that can be pushed in. The higher you go, the quicker they recharge (but also the more A/C amps they pull from your source).

The other thing I would highly recommend if you're going to start boondocking is a proper battery monitor. My favorite is the Victron BMV:
https://learntorv.com/victron-battery-monitor/

[Daebado]

Originally Posted by ependydad

You can upsize the converter because lithium batteries can take faster charges. Check the specs on whatever one you're looking at to see the maximum amount that can be pushed in. The higher you go, the quicker they recharge (but also the more A/C amps they pull from your source).

The other thing I would highly recommend if you're going to start boondocking is a proper battery monitor. My favorite is the Victron BMV:
https://learntorv.com/victron-battery-monitor/

I'm looking at the SOK 12V 100Ah. It says max charge current is 50A so is a 60A converter overkill or can you go just a bit higher than the battery rating?

Also, if I'm pulling from a 30A source, how will that affect the performance of the converter? will the converter continually trip my breaker? Do I need to buy a 30A converter instead? The 60A converter I mentioned above says it has an input of 130V A/C at 1025W. Unless A/C is calculated differently than DC, that should only be about an 8A draw from my source, right?

Some of this stuff makes total sense and some of it just gets downright confusing!

[CHICKDOE]

Yes you need to differentiate between ac amps and dc amps. Ac amps are at 120vac. Dc amps are at 12 vdc. A rule of thumb is that 1 ac amp is equivalent to 19 dc amps. So that converter that outputs 60 dc amps is drawing in 6 ac amps. This is approximate and ignores any load creat deny the converter itself.

[Daebado]

Originally Posted by CHICKDOE

Yes you need to differentiate between ac amps and dc amps. Ac amps are at 120vac. Dc amps are at 12 vdc. A rule of thumb is that 1 ac amp is equivalent to 19 dc amps. So that converter that outputs 60 dc amps is drawing in 6 ac amps. This is approximate and ignores any load creat deny the converter itself.

So, that's good to know but 6A or 8A... my questions remain the same.

[ependydad]

Originally Posted by Daebado

I'm looking at the SOK 12V 100Ah. It says max charge current is 50A so is a 60A converter overkill or can you go just a bit higher than the battery rating?

Also, if I'm pulling from a 30A source, how will that affect the performance of the converter? will the converter continually trip my breaker? Do I need to buy a 30A converter instead? The 60A converter I mentioned above says it has an input of 130V A/C at 1025W. Unless A/C is calculated differently than DC, that should only be about an 8A draw from my source, right?

Some of this stuff makes total sense and some of it just gets downright confusing!

The 60amp converter will be fine as the wire sizes and distance to the battery are far enough that you'll never actually see 60 at the batteries.

Pulling from a 30amp campsite won't be a problem but you will need to be mindful that 6-8 A/C amps can potentially be used by your converter at any given point. The same as your water heater may kick on at the same time you're running the air conditioner and microwave. It just becomes another thing to be aware of.

You do not need to buy a 30amp converter. The amps for converters are at 12v.

[TitanMike]

Originally Posted by Daebado

I'm looking at the SOK 12V 100Ah. It says max charge current is 50A so is a 60A converter overkill or can you go just a bit higher than the battery rating?

Definitely not overkill. If the charging battery draws 50 amp then there's some capacity left over to run 12 volt accessories at the same.

The main concern when going to LiFePo4 batteries is to make sure the wiring between the battery and converter is capable of carrying the full charging current.

If you don't upgrade this wire to a heavier gauge you need to make sure that the inline circuit breaker is at least the max rating for the existing wire size. A LiFePo4 battery will easily draw 50 amp to charge and do so for a long time. You want to make sure that the circuit breaker (often hidden between battery and power panel/converter doesn't trip with the continued high current. Most trailers/RV's have a #8awg wire which can handle up to 70 amp if it's NOT part of a wire bundle or in a conduit. If the existing circuit breaker is considerably less, I'd upgrade to at least a 50 amp.

[Daebado]

Originally Posted by TitanMike

Definitely not overkill. If the charging battery draws 50 amp then there's some capacity left over to run 12 volt accessories at the same.

So, would it be better then to go with the 80A converter to give myself a little extra headroom?

[TitanMike]

If you are installing a single LiFePo4 battery then you need to stay within the charge rate recommended by the battery manufacturer. That would be 50 amps for a 100 ah battery. The 60 amp converter won't really damage the battery as other loads and wire resistance will keep the charhe rate close to that.

If you installed two batteries the acceptable charge rate will then be 100 amps and only then would I recommend a larger converter.

There are times the extra resistance in the charge wire to the battery is a plus. This is one, keeping charge rate in line with recommendations.

Originally Posted by Daebado

So, would it be better then to go with the 80A converter to give myself a little extra headroom?

[CHICKDOE]

double check on what is required to upgrade to an 80 amp converter. i'm not sure what size you currently have but it is probably on a 15 amp 120 volt ac circuit. the 80 amp converter requires a 20 amp 120 volt ac circuit. so right there you would need to replace a circuit breaker and 120 volt cable feeding the converter.

then the dc cabling from the converter to the batteries would need to be verified and possible upgraded to handle the increased amperage the converter could supply to the batteries.

i'm not saying don't do it. just double check to make sure you can handle the increased amperage going into and out of the converter.

[itat]

Daebado, if I were doing what you’re doing, I’d get a lithium rated charger (Progressive Dynamics or Boondocker brands) with an AC plug and mount it close the batteries to keep the DC wiring as short as possible. Then I’d wire up a 120VAC receptacle beside the new charger so I can just plug it into the RV’s AC system. What that, you can charge the batteries when you’re plugged into a pedestal or at home or even just plug the charger into a generator if you have one.

[Daebado]

Thanks everyone, great advice, ideas and suggestions!

My struggle now is whether or not I should go ahead with this project or put it all on hold as we are looking to replace this camper once it is paid off (in about a year).

When I first started researching this project, I thought it was a simple matter of buying a couple portable solar panels and a new battery and then I could easily switch them to the new camper when we got it.

The more I learn, the more I realize that this is a bigger project than I thought! Even keeping the solar panels portable, I am still looking at replacing the converter, installing a charge controller and inverter, replacing and/or installing a lot of wiring...
It just seems like this might be a lot of work only to have to remove it all in a short time, put it all back to factory and then start all over on the new camper.

Maybe I should just start with a generator!

Either way, you all have given me a lot to think about, not only in this thread but in quite a few others I’ve been reading in this forum as well. Thank you!

[itat]

Originally Posted by Daebado

Thanks everyone, great advice, ideas and suggestions!

My struggle now is whether or not I should go ahead with this project or put it all on hold as we are looking to replace this camper once it is paid off (in about a year).

When I first started researching this project, I thought it was a simple matter of buying a couple portable solar panels and a new battery and then I could easily switch them to the new camper when we got it.

The more I learn, the more I realize that this is a bigger project than I thought! Even keeping the solar panels portable, I am still looking at replacing the converter, installing a charge controller and inverter, replacing and/or installing a lot of wiring...
It just seems like this might be a lot of work only to have to remove it all in a short time, put it all back to factory and then start all over on the new camper.

Maybe I should just start with a generator!

Either way, you all have given me a lot to think about, not only in this thread but in quite a few others I’ve been reading in this forum as well. Thank you!

If you're certain that you'll be selling this trailer in about a year, then I'd hold off on doing a full solar install if that's your goal. You could swap out the batteries and install a charger next to them now. That should be an easy swap and replacement before you sell it. The LiFePO4 batteries and charger will be good for many years. Of course, in order to boondock, you'll also need to install an inverter to power your 120 VAC stuff.

[ependydad]

I put in 4 lithium batteries, an inverter, and upgraded my converter on my old RV. When I went to trade it, I pulled 3 of the 4 batteries out, took out the inverter + all wiring, and told the dealer that I'd be swapping their battery for mine and would be swapping the converter.

It was extra work, but I needed the extra power in the old rig.

[PhilFromMaine]

Originally Posted by Daebado

The DW and I are wanting to get more into boondocking and eventually want to add about 200W of solar to our hybrid Shamrock 23WS and replace my current flooded lead acid battery with 100Ah LiFePO4. Combined with charge controller, invertor, etc. along with a generator for cloudy days, this will be a significant expense and I want to do it one step at a time.

As a preface, most of our trips are small, 2 to 4 day trips within a 6 hour drive from home with an occasional 7 to 9 day big trip somewhere (this year, it's Colorado).

To get started, I think I want to replace my battery, first. I'm assuming my present converter/charger isn't made for Lithium batteries (I haven't looked yet but will once the weather warms up a little) so I'm looking at something like a PD9160ALV. The main question I have currently is, how do I know if this is the right size for my needs? They make a number of different models. This one is 60 amps but they make them bigger and smaller.

Also, is there anything else I should be considering at this time besides the converter?


Thanks

The biggest focus should be the batteries. Get as many AH as you can. 100AH is probably on the lean side. The best advice concerning charging rate is to call the battery manufacturer. IMO, the 50 Amp charging spec you mentioned is basically just a caveat so that you don't overload your wiring. Generally speaking, it is always best to follow the manufacturers specs.

There are wiring sizing charts on the WEB for this. These charts are based on the amp load and the distance between components such as, in your case, the distance between the converter-charger and the battery.

I like the suggestion above to get a converter and to lug it into a wall socket close to the battery and not necessarily at the power supply cabinet.

As far as it being complicated, it is not. Even I figured it out. Will Prowse's DIY Solar site helped a lot. https://www.mobile-solarpower.com/