Electric Power Update – Trying to Avoid Tripping the Generator

 

Plan A:

2800w peak generator

Didn’t work. Well not sufficiently that it was worth carrying around such a big generator.

Plan B/C :

Charge cable from the truck alternator.

Works and is great if you just need to get a bit of power and it’s cold and raining outside. Running a 6.7L motor is not the most efficient way to charge the battery though. Works when we are driving however the fuel economy still takes a hit. Nothing for nothing.

Plan B/C:

Lots of solar.

Well the problem is that five laptops, two internet routers, an electric fridge and associated standby loads draw a lot of power and North America is not always sunny. We never seem to stay anywhere long enough or established enough that it is worth tilting the panels for the extra 30% power that would offer in winter. The result was that the two 100Ah AGM batteries we had regularly went flat and eventually one was giving up and we were only getting about 40Ah out of it.

Back to plan A:

Generator

I bought an 1800w load rated generator for the purpose of just charging the battery. It does this, however trips whenever someone forgets we are on the generator and puts on the microwave or even an extra laptop when charging the battery at full capacity. It will run the AC of the truck camper as it is only 9000BTU however again very careful attention to loads required or it will trip.

Plan D:

Lithium Batteries

We have now replaced the failing AGMs with fifteen parallel connected 10Ah 7S3P 18650 Li-Ion scooter batteries. This was cheaper than single larger lithium batteries and has more redundancy and upgradeability. I also individually loosely covered each battery with a welding blanket just in case. With the addition of another lithium battery I built earlier we now have about 160Ah of Lithium battery storage. With a bit of addition from the solar even on cloudy days we can now run for at least a couple of days without starting the generator. As the batteries are lithium, they can accept fast charging so when we do start the generator, we can charge the battery in a few hours.

Plan E:

High capacity charger.

Now that we are on plan E the thought of burning the place down has also crossed my mind again so more circuit breakers also coming.

The existing inverter charger can charge at up to 60 amps which is great however also adds any 120v loads on top so if we are charging at 60amps (1800w) any additional loads will trip the generator or grid power.

My idea is to separate the charging system from the AC power supply. I have ordered a 50A fully adjustable charger that can accept voltage inputs from 90v to 260v. My idea is that I will no longer directly power the camper from the grid / generator. All AC loads will be powered from the inverter and the new high-power battery charger will supply the inverter and battery with DC power. If the site in Mexico can only supply 10 amps at 90 volts then I can adjust the output of the charger to the available 900 watts continuous charge. The inverter will still supply up to 3000 watts intermittently to run the air conditioner or microwave and during the off cycle the battery will be replenished by the continuous charger. Some countries in South America are also 220V so we would have needed a transformer of some description anyway. Now hopefully, I can just leave the AC input supply to the inverter off and the universal input voltage of the charger will take care of the rest.

There are solar inverters with “Grid Boost” which would basically do what I am trying to do however they are expensive – particularly since I already have a good solar inverter and they don’t handle 120v and 240v inputs. There is also now a new MPP Solar inverter that is continuous AC to DC to AC which is essentially what I am doing but too late for me.

It is not the most efficient system. When running from the inverter generator, the generator produces DC power which is inverted to AC power which will now be converted back to DC power and then inverted back to AC power again. Of course, there are losses associated with each conversion. Fuel for the 80cc generator is cheap in the USA and at campsites the current limited supply is included. If I can manage to run everything without trips and overloads, I think it will be worth it. I will let you know.

The high capacity charger from China is now on go slow due to Corona virus. So, I have now installed an interim charger. This accepts 90v to 240v inputs and adjustable voltage however does not have current control just as per demand up to 40 amps. Still 40A x 30v is only 1.2kw which is 10A at 120v AC input so not too high. When the new one comes from China this will be kept as backup.

All installed now and tested today. Ran the AC and electric hot water at the same time as the kids were running the electric heater on low next door in the trailer. Yay didn’t trip the 30A circuit breaker.

All good now until the next update. Only disappointment the fan is a bit noisy.

Power is a bit like money.  No matter how much you have, you can always spend it and you always wish you had a bit more.