using a solar charger to regulate battery?

[Orlen Wolf]

Originally Posted by Ironhinge

Although it sounds like it is unnecessary from your experience, if someone with a setup like yours wished, they could protect the battery from overcharge during long-term storage by disconnecting the 4a from the simplex.

When you disconnect the AC power or turn off the Samlex battery charging stops so you don't have to disconnect the battery from the system. Also, a flooded lead-acid battery will not overcharge if the charge voltage is kept at 13.8V. The current supplied will be just enough to offset the natural self-discharge of the battery. Of course is is a good idea to disconnect the battery if the trailer will be in long-term storage. And make sure the battery top is clean. Sulfuric acid is conductive and even a thin layer on the battery top will allow the battery to self-discharge quicker. If the camper will be stored for more than three months try to arrange to charge the battery during storage.

Regarding intelligent, smart or three-stage chargers - They charge a battery in three steps, bulk, absorption and float.

In bulk charge the charge is current limited, usually at C=0.1 to C=0.5 with C being the battery capacity. This is also called a fast charge mode where a completely discharged battery is brought back to almost full charge (about 80%) in 2 to 6 hours.The problem is heat, the enemy of all things electrical or electronic. You are limited by I squared R with the R being the internal resistance of the battery. Heat dissipated goes up as the square of the charging current and, if not controlled, can literally cause the battery to melt down. The internal resistance of the battery also tends to increase as the charge rate increases so the problem is compounded. High charge rates can also cause the lead plates to disintegrate due to gas bubbles forming in enclosed areas in the plates.

In the absorption step the charge is voltage limited (usually at about 13.6 to 13.8V). This brings the battery up to full charge (from 80% to 100%) slowly but is more efficient overall as the charge current is much lower (lower I = less internal heating of the battery).

The final step is float mode where the battery no longer accepts a charge. It is full, satisfied and happy. This is the point where current flow to the battery is just enough to offset the self-discharge rate of the battery. Some chargers detect when the charge current drops below a threshold and then lowers the voltage a couple of tenths of a volt.

The Samlex really only uses the absorption and float mode since the initial charge rate is well below 0.1C (for a 100AH battery). Although it takes longer to charge a fully discharged battery this way it is much easier on the battery since there is less heating per unit time and more time to dissipate the heat. A cool battery is a happy battery!

There is another charging mode called equalizing where the battery is hit with a higher voltage per cell and a much higher current. This mode is normally only used with large stationary battery banks such as telephone switchboard cells. The charge is held until the cells are liberally gassing to ensure that all cells in the system are at 100%. Although I have heard of people using this mode on batteries in RVs I do not believe it is a good idea for the relatively small batteries we use. In addition to the heat generated there is the danger of exploding hydrogen gas. Just a little spark and you have battery pieces and sulfuric acid flying everywhere.

Some smart chargers use sensing circuitry to determine when to switch from bulk to absorption to float modes. Since the Samlex doesn't use the battery slaying bulk charge mode it isn't necessary.

The only downside of this system is that it takes longer to recharge a completely discharged battery. But you wouldn't let your battery get completely discharged would you?

Sorry to be so verbose but the above dissertation only scratches the surface of battery charging science. Whole books have been written on the subject.

73 for now
Orlen

[Orlen Wolf]

Originally Posted by steve dunham

You can only transform AC . You cannot transform DC
IE: There is no such animal as a DC transformer !!

Of course not. Such a device is called a DC to DC converter.

[redbarron55]

the Bogart is a great system. It measures the amps used and replaces them.
Good for tracking the battery condition etc.
When talking with them they thought about using other sources of current and said they thought that there was no reason they could think of that it would not work.
I considered using their system instead of the unit I bought to handle the charging. I bought the PD4045 because it had so many 12 volt fused circuits and I used a bunch of them so that a problem on one would not take out much with it.
Still I like the Bogart for a small solar system. I would like to have 200 - 250 watts installed.

[gordon2]

I think Progressive Dynamic converters (chargers) are the most common in FG trailers.. and they say this:
Q: Can I connect a solar panel to my batteries without harming the Converter/Charger?
A: Yes, adding a solar panel will not adversely affect our Converter/Chargers.

So (IMHO, I'm no expert) there no need to run the shore power charger though the solar charger, nor is there any benefit. Good idea to use the TriMetric meter to measure the current in and out of the battery from all your charging sources and all your loads.

[Raz]

Originally Posted by Orlen Wolf

When you disconnect the AC power or turn off the Samlex battery charging stops so you don't have to disconnect the battery from the system. Also, a flooded lead-acid battery will not overcharge if the charge voltage is kept at 13.8V. The current supplied will be just enough to offset the natural self-discharge of the battery. Of course is is a good idea to disconnect the battery if the trailer will be in long-term storage. And make sure the battery top is clean. Sulfuric acid is conductive and even a thin layer on the battery top will allow the battery to self-discharge quicker. If the camper will be stored for more than three months try to arrange to charge the battery during storage.

Regarding intelligent, smart or three-stage chargers - They charge a battery in three steps, bulk, absorption and float.

In bulk charge the charge is current limited, usually at C=0.1 to C=0.5 with C being the battery capacity. This is also called a fast charge mode where a completely discharged battery is brought back to almost full charge (about 80%) in 2 to 6 hours.The problem is heat, the enemy of all things electrical or electronic. You are limited by I squared R with the R being the internal resistance of the battery. Heat dissipated goes up as the square of the charging current and, if not controlled, can literally cause the battery to melt down. The internal resistance of the battery also tends to increase as the charge rate increases so the problem is compounded. High charge rates can also cause the lead plates to disintegrate due to gas bubbles forming in enclosed areas in the plates.

In the absorption step the charge is voltage limited (usually at about 13.6 to 13.8V). This brings the battery up to full charge (from 80% to 100%) slowly but is more efficient overall as the charge current is much lower (lower I = less internal heating of the battery).

The final step is float mode where the battery no longer accepts a charge. It is full, satisfied and happy. This is the point where current flow to the battery is just enough to offset the self-discharge rate of the battery. Some chargers detect when the charge current drops below a threshold and then lowers the voltage a couple of tenths of a volt.

The Samlex really only uses the absorption and float mode since the initial charge rate is well below 0.1C (for a 100AH battery). Although it takes longer to charge a fully discharged battery this way it is much easier on the battery since there is less heating per unit time and more time to dissipate the heat. A cool battery is a happy battery!

There is another charging mode called equalizing where the battery is hit with a higher voltage per cell and a much higher current. This mode is normally only used with large stationary battery banks such as telephone switchboard cells. The charge is held until the cells are liberally gassing to ensure that all cells in the system are at 100%. Although I have heard of people using this mode on batteries in RVs I do not believe it is a good idea for the relatively small batteries we use. In addition to the heat generated there is the danger of exploding hydrogen gas. Just a little spark and you have battery pieces and sulfuric acid flying everywhere.

Some smart chargers use sensing circuitry to determine when to switch from bulk to absorption to float modes. Since the Samlex doesn't use the battery slaying bulk charge mode it isn't necessary.

The only downside of this system is that it takes longer to recharge a completely discharged battery. But you wouldn't let your battery get completely discharged would you?

Sorry to be so verbose but the above dissertation only scratches the surface of battery charging science. Whole books have been written on the subject.

73 for now
Orlen

Good post. Unfortunately the sales folks suppling the solar boom have most folks believing they need a 4 stage smart charger or their batteries won't last a year. Whats interesting is that more often than not most RV batteries are charged by the tow alternator. Raz

[Orlen Wolf]

Originally Posted by Raz

Good post. Unfortunately the sales folks suppling the solar boom have most folks believing they need a 4 stage smart charger or their batteries won't last a year. Whats interesting is that more often than not most RV batteries are charged by the tow alternator. Raz

Very true but most tow vehicle charge lines are too small to give a good charge. A good #6 lead and a voltage booster at the camper end will ensure a fully charged coach battery when you arrive at your destination.

The "stock" wiring on my Dodge used a #14 lead to the 7-way. Way too small for the job

[steve dunham]

Originally Posted by Orlen Wolf

Of course not. Such a device is called a DC to DC converter.

Read the original post !!

[Raz]

Originally Posted by Orlen Wolf

Very true but most tow vehicle charge lines are too small to give a good charge. A good #6 lead and a voltage booster at the camper end will ensure a fully charged coach battery when you arrive at your destination.

The "stock" wiring on my Dodge used a #14 lead to the 7-way. Way too small for the job

The only difference between having a 6 gauge charge line and a 14 gauge charge line is how long it will take to charge the battery. The charge line circuit can be reduced to two batteries in opposition with a resistor between them. The voltage drop is always the difference between the two batteries ( Kichhoffs voltage law) and the charging current is that voltage divided by that resistance (ohms law). For the typical Group 24/27 battery, a 10 gauge charge line should fully charge the battery in a few hours as long as nothing is on (like the fridge) in the trailer. Raz

[Mike Magee]

Orlen, what do you feel is the advantage of the Samlex over a common PD inverter? The cost isn't much different, so is it just that you prefer the slow, low-heat charging? Or is there more to it?

[Timber Wolf]

Originally Posted by Raz

For the typical Group 24/27 battery, a 10 gauge charge line should fully charge the battery in a few hours as long as nothing is on (like the fridge) in the trailer. Raz

In my admittedly limited (so far) experience my F-150 just does keep up with running the TF130 fridge while underway. I have not traveled more than 3 or so hours yet though but am OK (not really happy) with just breaking even getting to a destination fully charged if I left that way to begin with. I intend to install solar soon (this year) and since most roads are pretty sunny I should get my charging done that way without depending on the Ford.

[Raz]

Originally Posted by Timber Wolf

In my admittedly limited (so far) experience my F-150 just does keep up with running the TF130 fridge while underway. I have not traveled more than 3 or so hours yet though but am OK (not really happy) with just breaking even getting to a destination fully charged if I left that way to begin with. I intend to install solar soon (this year) and since most roads are pretty sunny I should get my charging done that way without depending on the Ford.

There are 4 variables: 1) alternator capacity. 2) total charge line circuit resistance. That's the total resistance between the two positive terminals added to the total resistance between the two negative terminals. 3. State of charge of the trailer battery. 4). Load on the trailer battery. The most favorable scenario to a fully charged trailer battery is maximizing 1 and 3 while minimizing 2 and 4. Everyone's situation is different. For some folks a 14 gauge charge line will work fine while for others no matter how large they make the charge line their battery will never charge. Like using a garden hose to fill a bucket with a 3 inch hole. Raz

Edit- Tim, if your battery is charged when you arrive at your destination it sounds to me your system is working fine.